Sen. Arlen Specter stunned both parties on Capitol Hill today when he announced he would switch his party allegiance to Democrat after 42 years as a Republican, including 28 as a senator from Pennsylvania.
Beyond the personal drama and implications for the Republican Party, which has endured major setbacks in the last two general elections, Specter's decision could potentially give Democrats the ability to break Republican filibusters in the Senate.
Specter called his decision to switch from Republican to Democrat "painful," and said he made the decision based on public and private polling in Pennsylvania that showed "the prospects for winning a Republican primary [in Pennsylvania] are bleak."
"As the Republican party has moved farther and farther to the right, I have found myself increasingly at odds with the Republican philosophy and more in line with the philosophy of the Democratic Party," Specter said at a news conference Tuesday afternoon.
Former Congressman Pat Toomey, a conservative Republican, officially entered the primary race against Specter just two weeks ago and was way ahead in polls.
"I'm not prepared to have my 29-year record in the United States Senate decided by the Pennsylvania Republican primary. This is a decision that has been reached gradually as I have traveled the state in the last several months. Specifically, I got my own poll results back last Friday and consulted with my campaign manager..." he added.
In a Quinnipiac poll last month, Specter trailed Rep. Pat Toomey, 27-41 percent, among registered Pennsylvania Republicans in a primary matchup for Specter's Senate seat. Among all Pennsylvania registered voters in that poll, Specter had a 29 percent favorability rating among Republicans, compared with 60 percent among Democrats and 41 percent among independents.
In a rather jovial mood at his press conference, Specter was asked about the votes he has cast that outraged liberals over the years -- especially his votes to confirm conservatives like Supreme Court Justice Clarence Thomas. In response, the new Democrat noted that he has voted 10,000 times.
"I don't expect everybody to agree with all my votes. I don't agree with them all," he replied.
Asked if he expected to "butt heads" with fellow Democrats on anything he said: "It all depends if my fellow Democrats are wrong and stupid."
He said Democratic leaders, including Pennsylvania Gov. Ed Rendell, have approached him about backing his candidacy in the state's 2010 Senate elections.
Republican colleagues were downtrodden after learning the news. Sen. John Cornyn, the Texas Republican who is in charge of getting more Republicans elected to the Senate in 2010, called Specter's decision, "political self-preservation."
The effect of his switch was immediately felt on Capitol Hill. Even before a press conference announcing his switch, Specter popped in to an Appropriations subcommittee hearing on the federal response to the swine flu outbreak. This morning he would have been the ranking member on that committee. But when he showed up, just before 2 p.m., he sat on the Democratic side of the room.
Later, he'll vote on whether to confirm Kansas Gov. Kathleen Sebelius as HHS Secretary. Republican opposition to Sebelius has been growing, particularly with regard to her support of abortion rights, which Specter also supports.
Specter himself is a two-time cancer survivor. He was diagnosed and underwent treatment for Hodgkin's disease last year. He recently published a book "Never Give In: Battling Cancer in the Senate" about dealing with the disease after his initial diagnosis in February 2005.
Republican National Committee Chairman Michael Steele said the move is to further Specter's own political interests, adding in a CNN interview that the Republican party looks forward to defeating him in 2010, if the Democrats don't do it first.
After a weekly caucus lunch for Republicans, at which they learned of Specter's defection and briefly saw their former colleague, Senate Republican leaders admitted they were unhappy losing a member, but argued that it has nothing to do with the national Republican Party rejecting moderates.
This is about local Pennsylvania politics and Specter's desire for "political self-preservation," they said.
"Well, obviously, we are not happy that Sen. Specter has decided to become a Democrat. He visited with me in my office late yesterday afternoon and told me quite candidly that he'd been informed by his pollster that it would be impossible for him to be reelected in Pennsylvania as a Republican because he could not win the primary; and he was also informed by his pollster that he could not get elected as an independent, and indicated that he had decided to become a Democrat," Senate Minority Leader Mitch McConnell, R-Ky., said.
McConnell said Democrats will have a dangerous capacity if they can reach 60 votes, which they may do if and when Al Franken takes the Minnesota Senate seat.
That scenario has looked more likely with court decisions over the contested Senate race in Minnesota, but Republicans are sure to drag out their challenges on behalf of former Sen. Norm Coleman, who has slightly fewer votes than Franken in that race.
"It certainly sets up the potential -- the potential -- for the majority, if it chooses to, to run roughshod over the majority -- over the minority, to eliminate checks and balances and the kind of restraint that Americans have historically wanted from their government," McConnell warned.
McConnell dismissed the impression given by Specter's defection that moderates don't feel comfortable as Republicans.
"I reject that out of hand," he said. "We have moderates in our conference who have an enormous amount of influence. I can tell you, and you know this, because you're around here all the time, there's a good deal of difference between a senator from Maine and Mississippi. But we have a broad party."
But discomfort had everything to do with Specter's decision as he decried Republicans in Pennsylvania for going too far to the right and rattled off several recent House races in which moderate Republicans were defeated in primaries by more conservative Republicans.
Cornyn explained away Specter's decision: "[Specter] was very candid to acknowledge that this was simply nothing more, nothing less than political self-preservation. ... So his only options were to leave the Senate or to switch parties, since he was determined or he was convinced he could not win as an independent."
Some Republicans reacted philosophically to the news of Specter's decision to leave the party. Sen. Lindsey Graham, R-S.C., a chief backer of Sen. John McCain's 2008 presidential campaign, said that while he was disappointed in Specter, the move should carry a lesson for Republicans.
"The situation in Pennsylvania highlights the dilemma facing the Republican Party," Graham said in a written statement. "Ideologically, we are a center-right party and I am committed to maintaining that position. However, for us to have national relevance we have to run and win in blue states. As a party we have to expand our base and diversify our membership while maintaining our fiscally conservative, limited government approach."
Sen. Harry Reid, D-Nev., welcomed Specter to the Democratic party, while stressing that bipartisan work will still be important in the Senate.
Saying that this is a time for the parties to reasses themselves, Reid added: "This is not a time to gloat or give high fives."
White House officials welcomed the news.
"I welcome my old friend to the Democratic Party. Senator Arlen Specter is a man of remarkable courage and integrity. I know he will remain a powerful and independent voice for Pennsylvania and the country," Vice President Joe Biden said in a statement.
President Obama called Specter shortly after receiving news this morning that Specter had switched parties.
"You have my full support," the president said, adding that he was "thrilled to have you."
Previously announced Senate candidate and former head of the National Constitution Center in Philadelphia, Democrat Joe Torsella, declared that he still intends to seek the Democratic nomination for Senate in Pennsylvania irrespective of Specter's announcement today.
"I decided to run for the United States Senate from Pennsylvania for one simple reason: I believe we need new leadership, new ideas, and new approaches in Washington. It's become obvious that the old ways of doing business might have worked for the special interests, but they haven't worked for the rest of us," he said in a statement. "Nothing about today's news regarding Senator Specter changes that, or my intention to run for the Democratic nomination to the Senate in 2010 -- an election that is still a full year away."
That could become a challenging run for Torsella, given the backing Specter is receiving from other Democrats, including Obama.
"If the president is asked to raise money for Sen. Specter, he is happy to do it," White House press secretary Robert Gibbs said at a briefing today. "If the president is asked to campaign for Sen. Specter, he is happy to do it."
ABC News' Huma Khan, David Chalian and Jake Tapper contributed to this report.