"Under these circumstances, anyone appointed by Gov. Blagojevich cannot be an effective representative of the people of Illinois and, as we have said, will not be seated by the Democratic caucus."
Video: Burris & Blagojevich address the media.
Obama struck the same tone.
"Roland Burris is a good man and a fine public servant, but the Senate Democrats made it clear weeks ago that they cannot accept an appointment made by a governor who is accused of selling this very Senate seat. I agree with their decision," the president-elect said in a statement.
Senate leaders, who were scattered for the holidays, immediately convened a conference call. Some involved in the call were wary of being seen as denying a black man a seat in a chamber where there are no blacks, according to two officials knowledgeable about the talks who requested anonymity in order to speak freely.
"We say this without prejudice toward Roland Burris' ability, and we respect his years of public service," the leaders wrote. But the issue is not about Burris, they said. "It is about the integrity of a governor accused of attempting to sell this United States Senate seat."
Rep. Bobby Rush, an Illinois Democrat who was invited to speak at Blagojevich's news conference, urged Senate leaders not to block Burris. In fact, he almost dared them to try to stop Burris' appointment.
"There is no rhyme or reason why he should not be seated in the U.S. Senate," Rush said. "I don't think any U.S. senator ... wants to go on record to deny one African-American from being seated in the U.S. Senate."
He told reporters that Senate Democrats should not "hang and lynch the appointee as you try to castigate the appointer."
Blagojevich was arrested Dec. 9 after federal prosecutors allegedly recorded conversations in which he discussed appointing someone Obama favored in exchange for a position in the new president's Cabinet or naming someone favored by a union if he got a high-level union job.
The governor has faced a flood of calls for his resignation, and the Illinois House has begun impeachment proceedings. He maintains his innocence, and has vowed to stay in office.
Blagojevich's own lawyer said recently that there would be no point in the governor naming someone to the Senate because leaders there would reject his appointment.
Lt. Gov. Pat Quinn said Blagojevich's decision to appoint Burris is an "insult to the people of Illinois."
"We believe in clean government, and Rod Blagojevich has unclean hands," Quinn said.
Republican House Minority Leader Tom Cross compared Blagojevich to "a rabid dog in a corner who's just going to lash out."
Democratic state Rep. Monique Davis of Chicago, a member of the impeachment committee, said Burris' appointment will have no bearing on its decision.
"Anybody that wants to put the race card in there, they're playing with the wrong group of people. We're not going to operate that way, we're not going to deliberate that way, we're not going to say, 'Oh, look what a good thing he's done.' We're not going to do it," Davis said.
Illinois law gives the governor sole power to fill a Senate vacancy. Lawmakers considered stripping Blagojevich of that power after his arrest but could not agree on legislation - a fact the governor, who had said he would support a bill calling for a special election, pointed out Tuesday.
Blagojevich might have thought he could gain some legal advantage by making the appointment.
"He could think he's gaining leverage - that's not implausible," said Carl Tobias, a law professor at the University of Richmond in Virginia. "He's weaving these legal problems for Illinois, the Senate and the new administration. This is a mess."
White, the secretary of state who handles official paperwork, said he would not formally certify any appointment made by Blagojevich "because of the current cloud of controversy surround the governor."
It's not clear whether White's refusal would be enough to prevent a Blagojevich appointment from taking effect.
Burris is a native of Centralia in southern Illinois who graduated from Southern Illinois University before earning his law degree from Howard University.
He served as Illinois' comptroller from 1979 to 1991 and as the state's attorney general from 1991 to 1995. He also served as vice chairman of the Democratic National Committee from 1985 to 1989.
More recently, however, Burris has had a string of political disappointments.
He lost campaigns for the Democratic gubernatorial nomination in 1994, 1998 and 2002 - the last time losing to Blagojevich. In 1995, he was badly beaten when challenging Chicago Mayor Richard Daley as an independent.
Burris has been a consistent donor to Blagojevich in recent years.
He donated $1,000 to the Friends of Blagojevich fund in both 2004 and 2005, $1,500 in 2007 and $1,000 in June 2008, according to Illinois campaign finance data.