Washington (AP) - Pennsylvania Sen. Arlen Specter is a Democrat again, following a decades-long turn among Republicans. His defection that has the GOP warning about the perils of unchecked power only a few years after it controlled both the White House and Congress.
"The threat to the country presented ... by this defection really relates to the issue of whether or not in the United States or America our people want the majority party to have whatever it wants without restraint, without a check or balance," Senate Republican leader Mitch McConnell of Kentucky said Tuesday after Specter made his startling switch.
The move left Democrats with 59 votes in the Senate, and hoping that Al Franken can finally win a marathon recount in Minnesota and become their 60th. That's the number needed to overcome any Republican filibuster aimed at blocking President Barack Obama's ambitious agenda.
Even at their high point during President George W. Bush's presidency, when Republicans controlled both houses of Congress, they were well shy of 60 seats in the Senate.
But they brought the Senate to the brink of a crisis in 2005, when their leadership claimed the rules permitted them to confirm conservative judicial appointees by simple majority after they failed repeatedly to muster the strength needed to overcome Democratic filibusters.
A bipartisan group of senators eventually intervened to defuse the crisis. Sen. Harry Reid of Nevada was Democratic leader at the time, and McConnell was the second-ranking Republican in the Senate.
Specter was a Democrat until 1965, when he ran successfully on the Republican ticket for district attorney in Philadelphia. His switch Tuesday triggered something of a debate among Republicans, who lost not only the White House in 2008 but fell deeper into the minority in both the House and Senate.
Maine Sen. Olympia Snowe, one of a few remaining GOP moderates in the Senate, called Specter's decision another sign that the Republican Party needs to move toward the center.
"Ultimately, we're heading to having the smallest political tent in history, the way events have been unfolding," she said. "If the Republican Party fully intends to become a majority party in the future, it must move from the far right back toward the middle."
Countering, McConnell said Republicans have a broad party. "We have not done very well in the Northeast the last couple of years. We haven't done as well any places as we would like to have done in the last couple of years," he said.
"We intend to be competitive on a nationwide basis. I do not accept that we are going to be a regional party. And we're working very hard to compete throughout the country," he said.
Democrats, savoring Specter's switch as they celebrated Obama's first 100 days in office, couldn't resist taunting their rivals.
"I welcome Sen. Specter and his moderate voice to our diverse caucus," Reid, the majority leader, said in a statement.
Sen. Bob Menendez of New Jersey, head of the Democratic campaign committee, called the development "proof positive that the Republican Party is so out of touch with Americans that they're losing one of its most prominent leaders."
Specter told a news conference he did not intend to become an "automatic 60th vote" for Democrats trying to approve Obama's agenda of health care, energy and education by year's end. As evidence, he reaffirmed his opposition to legislation making it easier for workers to form unions, a bill that is a top priority for organized labor and backed by the White House and Democratic leadership in Congress.
No less an authority than Reid has attested to Specter's independence.
Specter "is always with us when we don't need him," Reid wrote in his 2008 autobiography, describing efforts to find Republicans willing to vote against the Iraq war.
Yet Specter cast one of only three Republican votes for the president's economic stimulus bill earlier this year, noting he concluded that without the legislation, the country ran the risk of an even deeper economic downturn than the one it is enduring.
At his news conference, Specter grew animated as he blamed conservatives for helping deliver control of the Senate to Democrats in 2006, a result he said made it impossible to confirm numerous judicial appointees of Bush.
"They don't make any bones about their willingness to lose the general election if they can purify the party. I don't understand it, but that's what they said," he added.
The five-term senator repeatedly cast his switch as a decision of principle. But he also said his own pollster had told him his chances of winning a Republican primary in Pennsylvania next year were bleak.
Sen. Mel Martinez, R-Fla., said that in a private meeting with Republicans, Specter "gave a purely political explanation. ... He said: 'I've looked at the polls. I can't win as a Republican, I can't win as an independent. The only way I have a shot is to be a Democrat.'"
As recently as late winter, Specter was asked by a reporter why he had not taken Democrats up on past offers to switch parties.
"Because I am a Republican," he said.
Associated Press writer Julie Davis contributed to this report.
Sen. Arlen Specter's party switch has the GOP warning about the perils of unchecked power only a few years after it controlled both the White House and Congress.