Specter, a Republican from Pennsylvania, is seeking his sixth term in the Senate, and said yesterday it was unlikely that he would win a GOP primary next year. He said conservatives are driving him and other moderates from the Republican Party.
"They don't make any bones about their willingness to lose the general election if they can purify the party," said Specter. I don't understand it, but that's what they say."
Specter's decision to become a Democrat means that if Democrat Al Franken is seated in the Senate, Democrats will have a 60-vote majority -- enough to overcome a filibuster.
Republican Norm Coleman has appealed a lower court ruling that Franken won last year's election to the Minnesota Supreme Court. Coleman's campaign released a statement saying it wants every valid vote counted.
Franken's campaign says Franken looks forward to working with senators from both parties. But the prospect of ending filibusters and advancing President Obama's agenda clearly thrills Democrats and scares Republicans.
"There may be a few votes over the course of the next couple of years in which that 60th Democratic vote can tip the balance," said Steven Smith, a political science professor at Washington University.
Smith said Specter's decision will intensify the spotlight on Minnesota's Senate race. He said Senate Republicans will continue to urge Coleman to challenge Franken's presumptive status as the winner.
If the Minnesota Supreme Court rules against his appeal, Coleman could challenge the election in federal court. Smith said Republicans nationally will be watching, and lobbying both Coleman and Republican Gov. Tim Pawlenty to deny Franken an election certificate.
"It does intensify the pressure on Minnesota Republicans to keep Al Franken out of the Senate," Smith said.
Right now the outcome of Minnesota's election comes down to six people -- the five members of the State Supreme Court who will hear Coleman's appeal, and Pawlenty, who will ultimately issue an election certificate to the winner.
Smith said it's likely that activists in both parties will give even more money to the Coleman and Franken campaigns to bolster their legal teams.
Pawlenty told reporters he doesn't expect any added pressure as a result of Specter's decision.
"The situation with Pennsylvania has no connection or impact on what's going to happen in Minnesota," he said.
Pawlenty again hedged on whether he'd issue the election certificate after the Minnesota Supreme Court weighs in on the race.
"What is clear is that the Minnesota Supreme Court has said the certificate of election cannot issue until the Minnesota Supreme Court process is concluded. So we just have to wait for that process and take our cues from the court," said Pawlenty.
For their part, Senate Democrats are downplaying the prospects of a filibuster-proof majority. Senate Majority Leader Harry Reid said Democrats will work to get bipartisan agreement on health care legislation and the budget. But he said he learned long ago that votes come one at a time.
"Every vote counts. Things haven't changed from how you count votes from that conversation I had decades ago to right now. Every vote matters," he said.