“I do,” Burris said with a grin as Vice President Dick Cheney administered the oath of office to the former Illinois attorney general who takes Obama’s place as the Senate’s only black member.

More than a week after his colleagues were sworn in, Burris was seated without objection or a roll call vote, even though Majority Leader Harry Reid had said senators would have their voices heard on whether to accept his appointment.

Reid smiled broadly and applauded as Burris received a standing ovation from his new colleagues and accepted handshakes and congratulations from Republicans and Democrats alike. Later, the senior senator from Illinois, Dick Durbin, was throwing a reception in his new colleague’s honor.

It was a warm welcome that contrasted sharply with last week’s treatment, when Burris showed up on Capitol Hill to be sworn in with his colleagues, only to be turned away by Reid and Durbin, the No. 2 Democrat in the Senate. They argued that Burris’ appointment wasn’t valid under Senate rules.

But as the scandal-scarred Blagojevich watched, Burris dug in and the two Senate Democratic leaders ultimately relented under pressure from Obama and rank-and-file Democrats who worried that the episode was distracting from more important matters and putting the party – and the president-elect – in a bad light.

“He is now the senator-designate from Illinois and, as such, will be accorded all the rights and privileges of a senator-elect,” Senate Majority Leader Harry Reid and Sen. Dick Durbin of Illinois said in a joint statement after Senate lawyers determined that Burris’ paperwork met Senate requirements to be seated.

The two senators said they expect Burris, a former Illinois attorney general, to be sworn in and seated this week, barring objections from Republicans.

The announcement is a major reversal for Senate Democrats. They initially balked at the surprise appointment by embattled Gov. Rod Blagojevich, who is accused by federal investigators of seeking to trade the Senate seat for personal favors, amid fears that any appointee would be tainted.

The blunders began when the Democrats, including President-elect Barack Obama, insisted they would not seat Burris as the Senate’s only black member because the appointment came from a governor accused of trying to sell Obama’ former seat.

On Wednesday, they all but admitted being outflanked by Illinois Gov. Rod Blagojevich, praising Burris and suggesting he soon will be a senator.

Eight days ago, Obama and Senate Democratic leaders saw Blagojevich as so politically damaged that they announced they would reject anyone he appointed to finish Obama’s term. Every Democratic senator signed a letter to the same effect.

Privately, key Democrats now admit they miscalculated from the start. They spent this week trying to backtrack and save face.

They had overstated their legal powers to block Burris’s appointment, they said, and failed to foresee the ability of Burris – a little-known Democrat with no apparent ties to Blagojevich’s misdeeds – to make himself a sympathetic figure in the national media.

Race complicated the matter, with many people asking how Democrats could prevent Burris from replacing Obama as the only black senator.

Underlying the Democrats’ initial response to Blagojevich’s appointment was a cold political calculation. Many felt that Burris, who unsuccessfully sought his party’s nomination for governor three times, would be a weak nominee when the Senate seat comes up for election in 2010. Knowing an incumbent senator can be hard to beat in a party primary, Senate Democrats had hoped to postpone acting on Blagojevich’s choice until if and when the governor was replaced, making it possible to put a more potent campaigner in the Senate seat.

Now, however, Democratic senators and strategists are reconciling themselves to the possibility of being stuck with Burris.

When Blagojevich, himself a Democrat, announced his choice of Burris on Dec. 30, Obama and Senate Democrats were fixated on the lurid accusations against the governor, according to interviews with several Democratic aides and lawmakers. Federal officials had arrested Blagojevich on Dec. 9, saying wiretaps caught him talking crudely of trying to sell the Senate seat to the highest bidder.

Top Democrats’ response was quick and nearly unanimous: Burris would never be seated because of the governors’ misdeeds.

“Anyone appointed by Gov. Blagojevich cannot be an effective representative” and “will not be seated by the Democratic caucus,” said Senate Majority Leader Harry Reid, D-Nev., and his top deputy, Sen. Dick Durbin, D-Ill.

Obama said, “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.”

Obama, Reid and Durbin are lawyers and among the nation’s highest-achieving politicians. Now, however, their initial comments seem unusually tone-deaf.

The ground shifted quickly beneath the Democrats, in several ways. Most importantly, the public’s focus moved from Blagojevich, who was easily vilified, to Burris, a likable if obscure politician whose highest office had been Illinois attorney general.

The more people learned about Burris, the more they saw him not fitting the story line of sleazy Chicago politics. From the start, Obama, Reid and others acknowledged that he apparently played no role in the governor’s bid for favors. As news accounts focused more on Burris than Blagojevich, the arguments against the appointment made less sense.

Meanwhile, the legal basis for opposing Burris came under greater scrutiny. Sen. Dianne Feinstein, D-Calif., had signed the letter opposing Burris’s appointment, but on Tuesday, the day Burris got turned away from the Capitol into a cold rain, she had a new view.

“Does the governor have the power, under law, to make the appointment?” she asked rhetorically. Yes, she answered, no matter how many accusations are lodged against him.

Sen. Patrick Leahy, a Vermont Democrat who chairs the Senate Judiciary Committee, phoned Reid last week to express concerns about the legal basis for barring Burris, and warned that the Democratic solidarity was crumbling.

On Monday, Obama and Reid spoke. Obama “conveyed the sense that if Burris has the legal standing to be seated, he should be, sooner rather than later,” said a transition official who could speak only on background because the conversation was private.

The Congressional Black Caucus was preparing to vote unanimously to support seating Burris.

On Wednesday, everything seemed changed. Reid warmly received Burris in his Capitol office, then told reporters he was waiting for the Illinois Supreme Court to decide whether the Illinois secretary of state had to sign off on Blagojevich’s appointment.

“I think it’s a pretty easy hurdle to get over,” Reid said of the remaining impediments to seating Burris.

A reporter asked whether Blagojevich had outmaneuvered him.

No, Reid said, recounting the governor’s arrest, vulgar language and wiretapped descriptions of the empty Senate seat as a gold mine to be sold.

“How are we supposed to react?” Reid asked, a bit plaintively. “We’ve acted in a very reasonable way.”

Talking to reporters on the second day of a Washington power odyssey that would intimidate many, the 71-year-old Burris declared himself “very happy” and said he was pleased with his meeting with Sens. Harry Reid and Dick Durbin.

“My whole interest in this experience is to be prepared” to lead Illinois, Burris said, “and very shortly I will have the opportunity to do that.”

Burris’ legal issues include a pending decision by a court in his home state on whether Secretary of State Jesse White’s signature is required on his certification papers and his appearance Thursday before a committee considering the impeachment of Gov. Rod Blagojevich, who appointed him to take Barack Obama’s Senate seat.

For his part, Obama stood above the fray, telling his own news conference that the decision on whether to allow Burris to join the Senate is a decision for Senate leaders. He did say that he knew him, liked him and would be happy to work with him if he is seated.

Earlier, Reid, D-Nev., emerged with Durbin from a private meeting they had in the Capitol building with Burris, the former attorney general of Illinois.

Reid said the Senate was awaiting that court ruling by the state court that tests whether the White has to put his signature on Burris’ letter of appointment. White has taken the position that Blagojevich, accused of seeking to benefit financially from filling Obama’s seat, did not have legal authority to make the appointment.

Of Burris, Reid told reporters: “We don’t have a problem with him as an individual.”

And both he and Durbin, D-Ill., dramatically softened their party’s opposition to seating any Blagojevich appointee.

Knowledgeable Senate officials said the visual embrace of Burris was meant to show acceptance of his personal and professional qualifications, an indication that opposition to seating him was waning.

Burris was on the second day of a bizarre introduction to Capitol Hill, standing in the rain Tuesday to say he wouldn’t be seated and then giving a much more upbeat assessment of prospects Wednesday after his meeting with Reid and Durbin.

Burris was asked about the obviously warmer reception he got the second time around this week.

“I don’t know what pressure they were under, but they, I guess they have to keep the integrity of the Senate,” he said. “And they did not want to rush into anything and make a decision where they have to then be trying to reverse that. And that would even be worse.”

Asked if he, Reid and Durbin discussed any conditions under which he could be seated, he said that subject “wasn’t even on their radar screen.”

When a reporter inquired as to whether Burris might have had any “pay to play” discussions with Blagojevich or his office, Burris said that couldn’t have happened “because I don’t have no money.”

Standing amid a huge throng of reporters and television cameras in a cold and steady rain, Burris, 71, declared that he had been informed that “my credentials are not in order and will not be accepted.”

The former Illinois attorney general said he was “not seeking to have any type of confrontation” over taking the seat that he was appointed to by embattled Gov. Rod Blagojevich. But Burris also said he was looking at options for taking the seat.

It was a spectacular demonstration of political gridlock at a time when the Democratic-controlled Congress has been eagerly awaiting Obama’s inauguration while nervously anticipating tense work on a much-discussed stimulus program to steady the faltering economy.

An attorney for Burris, Timothy W. Wright III, said that “our credentials were rejected by the secretary of the Senate. We were not allowed to be placed in the record books. We were not allowed to proceed to the floor for purposes of taking oath. All of which we think was improperly done and is against the law of this land. We will consider our options and we will certainly let you know what our decisions will be soon thereafter.”

Asked what his options were, Wright said there possibly could be a court challenge and he said that Burris also would continue to talk to the Senate leadership.

There had been earlier indications that the Senate would disallow Burris to take his seat, at least in part because his letter of appointment from Blagojevich was not co-signed by Illinois Secretary of State Jesse White.

Some of Burris’ supporters have bemoaned the fact that Democrats would stand in the way of the Senate gaining its only black member. Burris himself downplayed the issue of race, telling reporters: “I cannot control my supporters. I have never in my life, in all my years of being elected to office, thought anything about race.”

Earlier Tuesday, Burris had tense negotiations with Terrence Gainer, the Senate’s sergeant at arms.

“I’m presenting myself as the legally appointed senator from the state of Illinois. It is my hope and prayer that they recognize that the appointment is legal,” he said earlier in a nationally broadcast interview.

Burris dismissed the Senate Democratic leadership’s position that he cannot be seated because he was appointed by a governor accused in a criminal complaint of trying to benefit financially from his authority to fill the seat that Obama vacated after winning the presidential election.

Burriss said his belief is that his appointment is constitutional and that “I have no knowledge of where a secretary of state has veto power over a governor carrying out his constitutional duties.”

Burris also maintained that the announcement by Blagojevich Monday of a date for an election for a successor to Rep. Rahm Emanuel, D-Ill., proves the governor still has legal authority to carry out his duties. Emanuel will be Obama’s White House chief of staff.

“There’s nothing wrong with Roland Burris and there’s nothing wrong with the appointment,” Burris said.

Burris has found little support among fellow Democrats.

Senate Majority Leader Harry Reid, D-Nev., had said Monday that Burris would not be permitted to take his seat because Burris “has not been certified by the state of Illinois,” a reference to incomplete paperwork that only touches on the dispute. Senate Democrats maintain that Burris’ appointment is tainted because of the charges against Blagojevich.

While Blagojevich has signed formal appointment papers, White has not, and Senate rules require that signature. Burris, in turn, has gone to court hoping to win an order for White to sign the necessary paperwork, and he has also threatened to sue to take his seat in the Senate.