The proposed withdrawal would reduce the number of U.S. troops in Iraq to about 130,000 - the same as before the "surge" earlier this year aimed at reducing sectarian violence.

Congressional Democratic leaders criticized Mr. Bush's plan after a meeting with the president Tuesday. House Speaker Nancy Pelosi said it was "an insult to the intelligence of the American people."

General Petraeus and Ryan Crocker, the U.S. ambassador to Iraq, testified before House and Senate committees earlier this week. General Petraeus says the troop increase has led to decreased violence in Iraq, but he and Crocker cautioned against a premature withdrawal of U.S. forces from Iraq.

Iraq's national security advisor, Muwaffaq al-Rubaie, told reporters Wednesday that the number of U.S. troops could be reduced to 100,000 by the end of 2008. He says it would depend on the security threat within and outside the country, and the readiness level of Iraqi security forces.

Starting today, Thompson will spend the next week in the key early primary states of Iowa, New Hampshire, South Carolina and Florida.

He's betting he can make up for lost time and convince skeptics in his party that he's neither lazy nor underprepared, but instead methodical and getting in just as voters are ready to pay attention. All of his major competitors have spent months courting voters, raising money and refining their stances.

"He could catch fire and take off," said Cary Covington, an associate professor of political science at the University of Iowa. "But, historically, candidates who rely in Iowa on television ads and commercials don't do well. It takes organizing at the grassroots level and that takes time, and Thompson just doesn't have much of that time left now. He can't afford any mistakes. He has to hit hard and charge hard and really be running full blast."

Thompson has strengths going in. He's got celebrity and a homespun appeal as well as experience in national politics. He's also got a socially conservative message and reputation that could appeal to his party's base.

So far, Republicans have yet to solidify around any single competitor, be it former New York Mayor Rudy Giuliani, former Massachusetts Gov. Mitt Romney or any of the others.

Recent polls in early primary states show Thompson in second or third place among GOP candidates, in some combination with Giuliani and Romney.

Yet with his announcement, Thompson is off to mixed reviews.

Thompson's timing allowed him to avoid participating, literally by a few hours, in a televised Wednesday night candidate debate in New Hampshire. But his campaign bought time on Fox to air a 30-second Thompson spot during the debate.

That prompted New Hampshire's Republican Party chairman to accuse Thompson of wanting it both ways.

"I think New Hampshire voters and voters elsewhere would be forgiven for thinking he's skipping the debate because he isn't ready to have a substantive debate on the issues," chairman Fergus Cullen said. "And voters also could be forgiven for thinking, 'Well, what the heck was he doing all summer if he wasn't preparing?' There's a genuine interest here in Sen. Thompson and curiosity. But he seems to be getting off on the wrong foot."

Thompson's communications director Todd Harris defended the strategy. "We're not skipping debates," Harris said. "We're going to be present at a number of debates" in New Hampshire and other states in the weeks and months ahead.

"It's a question of how we've decided to roll out our campaign. And this is how we've decided to do it.

"Jay Leno is one of the highest-rated shows on television, and Sen. Thompson's message is going to be about bringing the country together under a banner of mainstream conservative change," Harris said. "You can't talk about unifying the country without talking to the entire country."

Harris describes Thompson as "the best communicator of the mainstream conservative message" in the GOP. "And our party needs a good communicator at a time when many in the public are not as high on the Republican Party as they used to be," he said.

An unbroken line of precedents dating back 220 years makes clear the Senate does not consider misdemeanor private conduct to be a fit subject of inquiry, asserted Washington attorney Stan Brand.

"We ought to seek to have the committee dismiss this outright," Brand said of a Senate ethics panel's investigation. "The Republican leadership called for an ethics investigation that had nothing to do with his office," said Brand on NBC's "Today" show.

Craig says he may still fight for his Senate seat, a spokesman says — if the lawmaker can clear his name with the Senate ethics panel and a Minnesota court.

The Republican lawmaker, who has represented Idaho for 27 years, announced Saturday that he intended to resign.

"It's not such a foregone conclusion anymore that the only thing he could do was resign," Sidney Smith, Craig's spokesman in Idaho's capital, told The Associated Press on Tuesday.

Mr. Bush’s visit to Iraq — his third — was spent at this remote desert base in the restive Sunni province of Anbar, where he had summoned Iraq’s Shiite prime minister, Nuri Kamal al-Maliki, and others to demonstrate that reconciliation among Iraq’s warring sectarian factions was at least conceivable, if not yet a fact.

After talks with Gen. David H. Petraeus, the top American commander in Iraq, and Ryan C. Crocker, the ambassador to Iraq, Mr. Bush said that they “tell me that if the kind of success we are now seeing here continues it will be possible to maintain the same level of security with fewer American forces.”

Mr. Bush did not say how large a troop withdrawal was possible. Nor did he say whether he envisioned any forces being withdrawn sooner than next spring, when the first of the additional 30,000 troops Mr. Bush sent to Iraq this year are scheduled to come home anyway.

Still, his remarks were the clearest indication yet that a reduction would begin sometime in the months ahead, answering the growing opposition in Washington to an unpopular war while at the same time trying to argue that any change in strategy was not a failure.

“Those decisions will be based on a calm assessment by our military commanders on the conditions on the ground — not a nervous reaction by Washington politicians to poll results in the media,” Mr. Bush told a gathering of American troops, who responded with a rousing cheer. “In other words, when we begin to draw down troops from Iraq, it will be from a position of strength and success, not from a position of fear and failure. To do otherwise would embolden our enemies and make it more likely that they would attack us at home.”

To ensure security, the White House shrouded Mr. Bush’s visit to Iraq in secrecy.

Mr. Bush flew with Secretary of State Condoleezza Rice and his national security adviser, Stephen J. Hadley, an extraordinary gathering of top leaders in a war zone. Defense Secretary Robert M. Gates and Gen. Peter Pace, the chairman of the Joint Chiefs of Staff, flew to Iraq separately and joined them.

The Anbar region is a Sunni stronghold where in recent months there have been significant improvements in security. Administration officials have been touting the gains as evidence that the increase in American troops has proved a success — a word Mr. Bush used eight times in his public remarks on Monday.

Mr. Hadley, briefing reporters, recalled a military intelligence officer’s dire warning a year ago that Al Qaeda controlled the provincial capital, Ramadi, and other towns in the region. “Anbar Province is lost,” he quoted the analyst as saying then. Mr. Hadley was apparently referring to Al Qaeda in Mesopotamia, the homegrown Sunni Arab extremist group that American intelligence agencies have concluded is foreign led. The extent of its links to Osama bin Laden’s network is not clear.

On Monday, after meeting with some of the local Sunni leaders who only months ago led the struggle against the American presence in the region, Mr. Bush held up Anbar as a model of the progress that was possible.

“When you stand on the ground here in Anbar and hear from the people who live here, you can see what the future of Iraq can look like,” he said, night having fallen at the base.

During his visit, Mr. Bush did not leave the base, a heavily fortified home to about 10,000 American troops about 120 miles west of Baghdad. Mr. Hadley said planning for the trip had started five or six weeks ago.

Administration officials rejected the notion that the trip was a publicity stunt. They said Mr. Bush wanted to meet face-to-face with General Petraeus and Mr. Crocker, who are to testify before Congress about progress in Iraq next week, and with Iraqi leaders he has been pressing from afar to take steps toward political reconciliation.

By summoning Mr. Maliki and other top officials to the Sunni heartland, a region the Shiite prime minister has rarely visited, Mr. Bush succeeded in forcing a public display of unity. The Iraqi officials there included President Jalal Talabani, Vice President Adel Abdul-Mehdi, Vice President Tariq al-Hashemi, Deputy Prime Minister Barham Salih and Massoud Barzani, the president of the Kurdistan region.

Iraq’s foreign minister, Hoshyar Zebari, who was visiting neighboring Iran when Mr. Bush and the other top administration officials arrived, was conspicuously absent. Mr. Zebari, a Kurd, said he had been aware that high-level visitors from the United States were coming but that his trip to Iran had been planned long in advance and that the timing was strictly a coincidence.

In Washington, a spokesman for Senator Harry Reid of Nevada, the Democratic majority leader, said the president’s visit and his assertions about progress would do little to persuade skeptics. “Despite this massive P.R. operation, the American people are still demanding a new strategy,” the spokesman, Jim Manley, said in a telephone interview.

Anthony H. Cordesman, a senior fellow at the Center for Strategic and International Studies, said the reversal in Anbar had less to do with American strategy than with local frustration over the extremism of Al Qaeda fighters trying to impose their doctrine. Mr. Cordesman suggested it was more of an anomaly than a model that could be applied elsewhere in Iraq, where sectarian divisions and strife appear to be worsening.

“We are spinning events that don’t really reflect the reality on the ground,” he said.

While some administration officials have recently described the Sunni shift in Anbar as serendipitous, they portrayed the improvements as an outgrowth, at least in part, of the decision to send nearly 4,000 additional marines to the province as part of the White House strategy to increase troops. “This is not serendipity,” Mr. Hadley told reporters.

Distrust remains deep between Sunnis in Anbar and the Maliki government — and it is clear that Mr. Maliki sees efforts by the American military to organize armed groups of Sunnis to assist American troops as a policy that amounts to assisting his enemies. Nor is it clear that the same model can be made to work in areas of Iraq where Sunnis and Shiites live together.

Sunnis, for their part, complain that the Maliki government has long failed to deliver services and to share oil revenue with Anbar. Describing the meeting Monday between the tribal sheiks and Iraqi officials from Baghdad, Mr. Gates said, “There was a sense of shared purpose among them and some good-natured jousting over resources.”

It remained unclear whether Mr. Bush planned to announce any specific troop withdrawals when he delivers the congressionally mandated report later this month.

Several administration officials say Mr. Bush and his commanders and military advisers have neared a consensus on beginning a reduction in American forces. Speaking to reporters traveling with him, Mr. Gates said Monday that he had formulated his opinion, though he declined to disclose it.

Asked about Mr. Bush’s comments on possible troop reductions, Mr. Gates added, “Clearly that is one of the central issues that everyone has been examining — what is the security situation, what do we expect the security situation to be in the months ahead?” He went on to say, “What opportunities does that provide in terms of maintaining the security situation while perhaps beginning to bring the troop level down?”

As he did in Washington late last week, Mr. Bush urged lawmakers to withhold judgment on the situation in Iraq until hearing first-hand reports next week from General Petraeus and Mr. Crocker. At the same time, though, he has used the White House’s considerable platform to assert his own views.

“The strategy we put into place earlier this year was designed to help the Iraqis improve their security so that political and economic progress could follow,” Mr. Bush said after meeting with Mr. Maliki and the other Iraqi leaders. “And that is exactly the effect it is having in places like Anbar.”

On Monday, at a news conference in Baghdad, Mr. Maliki made his own effort to underscore political progress his government had achieved in recent weeks. He said that a long-discussed law allowing former members of the Baath Party of Saddam Hussein to return to jobs in government had been submitted to Parliament.

“This law has been approved by the political leaders, and by the national political council,” Mr. Maliki said. “It is now before the parliament to discuss it and approve it.”

Agreement on the law, part of a package of requirements pressed by the Bush administration, would be an important milestone.

“We believe that this law represents the minimum accepted level of our ambitions,” said Salman al-Jumaili, a lawmaker from the main Sunni coalition.

An earlier agreement on a law broke down after Shiite leaders in southern Iraq voiced opposition.

Although no reason was given, Snow recently told conservative radio talk show host Hugh Hewitt that, due to financial reasons, he did not expect to remain on the White House staff through the remainder of President Bush's term.

Bush told reporters Friday that he will "sadly accept" Snow's resignation.

Flanked by Snow and Perino in the White House press room, the president spoke warmly of his departing press secretary.

"It's been a joy to watch him spar with you," Bush told reporters.

Bush said he was certain of two things in regard to Snow.

"He'll battle cancer and win," Bush said, "and he'll be a solid contributor to society."

Turning to Snow, the president then said: "I love you, and I wish you all the best."

Taking the podium, Snow said he was thankful for the opportunity to serve as press secretary.

"This job has been a dream for me -- and a blast," Snow said.

Snow's cancer was diagnosed for the first time in February 2005. His colon was removed, and after six months of treatment, doctors said the cancer was in remission.

Perino announced March 27 that Snow's cancer had recurred, and that doctors had removed a growth from his abdomen the day before.

Sources told CNN two weeks ago that Snow was planning to leave his job, possibly as early as September.

Snow, who had said he would leave his post before the end of Bush's second term, repeated that the decision is based on finances, not health. He took a major pay cut after leaving the world of cable television and talk radio to come to the White House.

According to The Washington Post, Snow makes $168,000 as the White House spokesman.

Bush tapped Snow to replace Scott McClellan in April 2006. Snow had been an anchor for "Fox News Sunday" and a political analyst for the Fox News Channel, which he joined in 1996. He also hosted "The Tony Snow Show" on Fox News Radio.

On Thursday, Snow told CNN his health is improving, citing two new medical tests this month which found the cancer has not spread.

"The tumors are stable -- they are not growing," Snow said of the results from an MRI and a CAT Scan. "And there are no new growths. The health is good."

The press secretary, whose hair has turned gray during chemotherapy treatment, said his black hair is expected to grow back in about a month.

"I'm also putting on weight again," he said after returning from a 10-day vacation. "I actually feel very good about" the health situation.

Snow said that on Friday he was to see his oncologist, and they will decide on some minor forms of chemotherapy to start as maintenance treatment.

They view his case as a prime example of hypocrisy -- a man who furtively engaged in same-sex liaisons while consistently opposing gay-rights measures as a politician.

" He may very well not think of himself as being gay, and these are just urges that he has," said Matt Foreman of the National Gay and Lesbian Task Force. " It's the tragedy of homophobia. People create these walls that separate themselves from who they really are."

The activist, Mike Rogers, went public last October with allegations that Craig engaged in sexual encounters with at least three men, including one who said he had sex with Craig twice at Washington's Union Station.

The Idaho Statesman went even further back into Craig's life, talking to other men who claimed they were solicited by him.

It also mentioned a scandal in 1982, in which a male page reported having sex with three congressmen, and Craig -- although not named by the youth -- issued a statement denying any wrongdoing.

Rogers noted that some politicians, when confronted with evidence about same-sex encounters, have acknowledged their homosexuality -- such as Rep. Barney Frank (D-Mass.) and the late Rep. Gerry Studds (D-Mass.).

Others persist in denial, and Rogers contends they are fair game for exposure if they vote against gay-rights causes.

''I'd love for Larry Craig to come out and be honest with the people of Idaho and run as a Senate candidate and see if the Republican Party is the big tent they claim to be,'' Rogers said.

Craig's political support was eroding by the hour Wednesday as fellow Republicans in Congress called for him to resign and party leaders pushed him unceremoniously from senior posts.

The White House expressed disappointment, and Senators John McCain (R-Ariz.) and Norm Coleman (R-Minn.) both joined calls for Craig to resign.

''My opinion is that when you plead guilty to a crime, you shouldn't serve. That's not a moral stand. That's not a holier-than-thou. It's just a factual situation," McCain said.