Blagojevich's appointment of former state Attorney General Roland Burris injected race into the drama surrounding the embattled governor, who repeatedly sought to distance his selection from charges that he tried to sell the seat to the highest bidder.
"Please don't allow the allegations against me to taint a good and honest man," the governor said, turning to the smiling 71-year-old standing by his side.
"This is about Roland Burris as a U.S. senator, not about the governor who made the appointment."
Burris was the first African-American elected to major statewide office in Illinois, serving as comptroller and running for governor three times - the last time losing to Blagojevich.
He said he has no connection to the charges against Blagojevich, who was arrested earlier this month.
Even before the announcement, which was leaked several hours before, the governor's move ran into opposition.
Illinois Secretary of State Jesse White, who must certify the appointment, said Tuesday he will not do so. And Senate leaders reiterated that they would not accept anyone appointed by Blagojevich.
In a statement Tuesday, Senate Democrats maintained that Blagojevich should not make the appointment because doing so would be unfair to Burris and to the people of Illinois.
"It is truly regrettable that despite requests from all 50 Democratic senators and public officials throughout Illinois, Gov. Blagojevich would take the imprudent step of appointing someone to the United States Senate who would serve under a shadow and be plagued by questions of impropriety," the statement said.
"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."
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, with Obama's departure, 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."
"Bobby Rush didn't play the race card, he dealt the whole deck," CBS News Senior Political Analyst Jeff Greenfield said. "He said, 'How can you not seat the only African American who will be in your body for something he didn't do?'"
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.