Spitzer was scheduled to announce his resignation midday, according to a second top Spitzer staffer. The officials spoke to The Associated Press on condition of anonymity because the announcement had not yet been made.

Spitzer and his wife, Silda, left their apartment around 11 a.m. and got into a black SUV to take them to his office. Cameras aboard news helicopters tracked the movement of Spitzer's three-vehicle motorcade from his apartment on the Upper East Side to his office in midtown Manhattan.

Spitzer would be replaced by Lt. Gov. David Paterson, who will become New York's first black governor.

The scandal erupted Monday when allegations surfaced that Spitzer, a 48-year-old married man with three teenage daughters, spent thousands of dollars on a call girl named Kristen at a swanky Washington hotel on the night before Valentine's Day.

"I have acted in a way that violates my obligations to my family and violates my — or any — sense of right and wrong," the governor said at a news conference with his wife at his side. "I apologize to the public, whom I promised better."

Calls for his resignation came immediately. Republicans began talking impeachment if he didn't step aside. Meanwhile, Spitzer stayed holed up in his Manhattan apartment, where he was reportedly weighing his options, including waiting to use resignation as a bargaining chip with federal prosecutors to avoid indictment.

The case involving Spitzer started when banks noticed frequent cash transfers from several accounts and filed suspicious activity reports with the Internal Revenue Service, a law enforcement official told The Associated Press. The accounts were traced back to Spitzer, leading public corruption investigators to open an inquiry.

A law enforcement official said Tuesday that Spitzer had spent tens of thousands of dollars with the call-girl service Emperors Club VIP. Another official said the amount could be as high as $80,000.

Still another law enforcement official said investigators found that during the tryst with Kristen, Spitzer used two rooms at Washington's Mayflower Hotel — one for himself, the other for the prostitute. Sometime around 10 p.m., Spitzer sneaked away from his security detail and made his way to her room, the official said.

According to an affidavit, a federal judge approved wiretaps on the escort service's telephone in January and February. FBI agents in Washington had the Mayflower under surveillance when Spitzer was in town, a senior law enforcement official said.

The officials spoke to the AP on condition of anonymity because of the sensitivity of the case.

Spitzer, a first-term Democrat, built his political reputation on rooting out government corruption, and made a name for himself as attorney general as crusader against shady practices and overly generous compensation. He also cracked down on prostitution.

He was known as the "Sheriff of Wall Street." Time magazine named him "Crusader of the Year," and the tabloids proclaimed him "Eliot Ness." The square-jawed graduate of Princeton University and Harvard Law was sometimes mentioned as a potential candidate for president.

He rode into the governor's office with a historic margin of victory on Jan. 1, 2007, vowing to stamp out corruption in New York government in the same way that he took on Wall Street executives with a vengeance while state attorney general.

His term as governor has been fraught with problems, including an unpopular plan to grant driver's licenses to illegal immigrants and a plot by his aides to smear his main Republican nemesis. The prostitution scandal, some said, was too much to overcome.

Barely known outside of his Harlem political base, Paterson, 53, has been in New York government since his election to the state Senate in 1985. He led the Democratic caucus in the Senate before running with Spitzer as his No. 2.

Though legally blind, Paterson has enough sight in his right eye to walk unaided, recognize people at conversational distance and even read if text is placed close to his face. While Spitzer is renowned for his abrasive style, Paterson has built a reputation as a conciliator.

At a morning news conference, Senate Majority Leader Joseph Bruno, Spitzer's chief rival, said he had not yet heard from the governor but that he was moving on with the business of the state. Lawmakers were set to vote on budget bills Wednesday afternoon.

"We are going to partner with the lieutenant governor when he becomes governor," said Bruno. "David has always been very open with me, very forthright ... I look forward to a positive, productive relationship."

Bruno, though the next highest-ranking official, does not become lieutenant governor upon Paterson's ascension to governor. The lieutenant governor's office would remain vacant until the next general election in 2010 under state law. However, whenever Paterson is out of state or if he were to become incapacitated, Bruno would be acting governor.