Burris would be relying on a constitutional provision listing just three, easily met qualifications for the job and a 1969 Supreme Court decision rebuking the House for excluding an elected, though scandal-tarred, lawmaker.

So far, Senate leaders are unwilling to seat Burris because he was named by Illinois Gov. Rod Blagojevich, ensnared by allegations of corruption, to replace President-elect Barack Obama in the Senate.

Democrats and Obama have said the federal corruption charges against Blagojevich would strip credibility from anyone he appointed to the seat, although they do not question the integrity of Burris, a former Illinois attorney general. Blagojevich denies federal accusations that he tried to sell Obama's seat.

Senate Democrats are relying for the moment on a technicality — the refusal of the Illinois secretary of state to sign paperwork making Burris' appointment official. Burris' lawyers first are asking the state Supreme Court to take care of that problem.

But it is far from clear that Senate Majority Leader Harry Reid, D-Nev., would then relent and welcome Burris as a new colleague.