Sen. Arlen Specter, R-Pa., will announce this afternoon that he is switching to the Democratic Party.
He's taken an all-but-sure loss in the Republican primary into an almost sure hold on his seat in 2010.
Assuming Al Franken takes the Minnesota Senate seat, Democrats will have that magic number of 60 Senate votes.
Some background from the White House:
At 10:25am, while in the Oval Office and during his economic daily briefing, the president was handed a note that said “Specter is announcing he is changing parties."At 10:32am, President Barack Obama reached Specter and told him "you have my full support."
Obama told Specter, "thrilled to have you."
In a written statement today, Specter wrote, "Since my election in 1980, as part of the Reagan Big Tent, the Republican Party has moved far to the right."
"Last year, more than 200,000 Republicans in Pennsylvania changed their registration to become Democrats. I now find my political philosophy more in line with Democrats than Republicans. When I supported the stimulus package, I knew that it would not be popular with the Republican Party. But, I saw the stimulus as necessary to lessen the risk of a far more serious recession than we are now experiencing," Specter wrote.
Specter was facing an uphill primary challenge from former Rep. Pat Toomey, R-Penn.
The Pennsylvania senator trailed Toomey 27-41 percent, according to a Quinnipiac poll last month among registered Pennsylvania Republicans.
Teddy Davis of ABC's political unit adds this from Pennsylvania Governor Ed Rendell:
At a March 12 lunch with reporters in Washington, DC, attended by ABC News, Pennsylvania Democratic Gov. Ed Rendell paid tribute to Specter's general-election appeal, saying, "I have no interest in being senator but I couldn't beat Arlen in a general. We don't have anyone who can beat him in a general right now.""If Specter wins the primary, it's a huge uphill fight" for the Democrats, Rendell added.Despite Specter's general-election appeal, however, he faced a tough fight in the GOP primary against former Rep. Pat Toomey, R-Pa., who recently stepped down as the head of the anti-tax Club for Growth.Part of the reason why a potential Republican primary was becoming so tough for Specter is that the hard-fought 2008 Democratic primary in the state between Obama and now Secretary of State Hillary Clinton thinned the Pennsylvania GOP of many of its moderate voters who switched their party registration to Democratic so they could help influence the Obama vs. Clinton race.--George Stephanopoulos