If state law does not (or cannot) stand in the way, can Harry Reid and the Democratic caucus make good on the promise not to seat a Blagojevich appointee? Article I, Section 5 of the Constitution says: "Each House shall be the Judge of the Elections, Returns and Qualifications of its own Members." Until 40 years ago, there was little doubt that the Senate could have refused to seat a would-be senator, however valid the process of his selection. But in 1969 the Supreme Court decided Powell v. McCormack, holding that the House of Representatives could not deny a seat to a duly elected person who met all the Constitution's qualifications and suffered from none of its disabilities.
I think Powell was wrongly decided—for reasons irrelevant here—but it is generally accepted as an authoritative gloss on the power of either house of Congress to deny a seat to a validly chosen would-be member. Rod Blagojevich has treated Harry Reid's threat like a bluff he is now calling. My bet is that Reid will fold.
Gosh, it sucks to be a Democrat right now.
Of course, there is an out. President-Elect Obama could call on Roland Burris to withdraw his name from consideration until Illinois straightens out its act. Let's see what the Big Kahuna decides to do.
