Five-term GOP Sen. Arlen Specter said Tuesday that his party had "gone too far to the right" and he would defect to the Democrats. But he promised to maintain his independence and not be an "automatic" vote for his new party.
Specter, 79, said in a statement that he had surveyed his supporters and officeholders in Pennsylvania and it had "become clear" that his support of the White House stimulus package had "caused a schism which makes our differences irreconcilable."
Later, appearing for a news conference in Washington, he said in a reference to a likely 2010 Republican primary challenge that he was "not prepared to have my fate decided by that jury."
"I know I disappoint my friends and colleagues," he said. "But, frankly, I have been disappointed by some of the response. So, the disappointment runs in both directions."
Specter was one of only three GOP senators to vote for President Obama's stimulus bill. Widely viewed as among the most moderate GOP lawmakers, Specter had found himself at odds with the party line on several times over the years, particularly over his support of abortion and gay rights.
With Specter, Democrats would have 59 Senate seats. Minnesota Democrat Al Franken, whose election is still in question months after voters went to the polls, could become a 60th vote, giving the party the number it needs to block filibusters by GOP senators.
Specter, however, took pains to say he would maintain his hallmark independence.
"I will not be an automatic 60th vote," he emphasized. "I have always agreed with John Kennedy that sometimes a party asks too much. And if the Democratic Party asks too much, I will not hesitate to disagree."
President Obama telephoned Specter to offer his "full support," saying the Democratic Party was "thrilled" to have him, The Associated Press reported. The senator said Vice President Biden had recently urged him to become a Democrat.
Specter, whose likely opponent in the 2010 GOP primary would have been former conservative Rep. Pat Toomey, had publicly acknowledged that to win, he would need thousands of Pennsylvania voters who had switched from Republican to Democrat in last year's presidential election to vote for him.
Senate colleagues in the Republican Party reacted with either disappointment or resignation, while Democrats welcomed a new member to their caucus.
Arizona Sen. John McCain expressed his regret. "I think it's pretty obvious the polls showed him well behind his primary opponent," the former GOP presidential candidate said.
Sen. Saxby Chambliss (R-GA) said he was "disappointed" at the decision.
"Arlen's a good friend, a great guy." he said.
Asked if he was surprised by the move, Iowa Democratic Sen. Tom Harkin said: "I'm surprised it happened this quickly. I thought it might have to germinate a little bit longer," before adding, "But, this is fine."
The move, however, left others wondering about the future of a party that has increasingly edged out moderate voices.
Maine Sen. Olympia Snowe said she has also been wooed by Democrats but has "no plans" to do the same as Specter. She nonetheless expressed concern over the direction of her party.
"The statements that are coming nationally from the Republican Party ... nurture a culture of exclusion and alienation," she said. "I really think this is a time for the Republican Party to ... re-evaluate and redefine."
As one of the most senior Republicans in the Senate, Specter enjoyed powerful posts on the Judiciary and Appropriations panels. Democrats must now decide how much seniority he gets credit for in their committee assignments.
From NPR and wire service reports