WASHINGTON (CNN) -- Reaction on Tuesday to Pennsylvania Sen. Arlen Specter's switch from the Republican to the Democratic Party ranged from barely concealed glee to dismay among Senate colleagues and elites from both parties.
Republican Party Chairman Michael Steele said Specter left because he knew he'd lose in the primary.
Some interpreted the move as a political calculation, others as a principled decision.
Most saw it as inevitable.
"I regret his decision, but he obviously saw the handwriting on the wall that he could not win in Pennsylvania as a Republican," said Sen. Christopher "Kit" Bond, R-Missouri.
In his announcement, Specter noted that 200,000 voters in Pennsylvania had switched their party registration from GOP to Democrat.
"The bottom line is the Republican Party has become inhospitable to moderates,'" said Sen. Charles Schumer, D-New York. "It was just very uncomfortable for Arlen Specter. He was being challenged on the right. When he did what he thought was principled, he was scorned by the overwhelming base of his party."
Republican Party Chairman Michael Steele said principles had nothing to do with the moderate Specter's switch.
"He left to further his personal political interests," Steele said, "because he knew that he was going to lose a Republican primary due to his left-wing voting record. Republicans look forward to beating Sen. Specter in 2010, assuming the Democrats don't do it first."
Sen. Olympia Snowe, R-Maine, like Specter a moderate, said the news was "devastating" on both a personal and partisan level.
"I've always been concerned about the Republican Party nationally, about their exclusionary policies towards moderate Republicans," Snowe said. "That's not a secretly held view on my part."
Snowe and Specter were two of only three Republican senators (including Susan Collins of Maine) to vote with the Democrats on the stimulus package, which stoked the ire of conservatives.
Among them was radio commentator Rush Limbaugh, who said the GOP moderates have it all wrong.
"It's just the exact opposite. The right wing has gone away," Limbaugh said. "The conservative movement is being shut out of the Republican Party. The Republican Party is more like Arlen Specter than it has ever been." Watch response of Senate Minority Leader Mitch McConnell »
The Obama administration responded warmly to the move. White House spokesman Robert Gibbs said the president was "thrilled to have him in the Democratic Party" and that Specter had his "full support."
"I think Sen. Specter made a decision today about how he can best represent the people of Pennsylvania in the United States Senate," Gibbs said. "He was a valuable ally in passing the Recovery and Reinvestment Act that's now the law of the land, and we're appreciative of his support." Watch White House spokesman Robert Gibbs' comments »
Senate Majority Whip Dick Durban, D-Illinois, said the move was "a major deal, and it moves us one step closer to the votes we need to pass major legislation."
Specter's fellow Pennsylvanian, and now fellow Democrat, in the Senate agreed:
"I think it's good news that President Obama's priorities this year are going to have more support than they would have otherwise," said Sen. Bob Casey. "It will make it more likely that the agenda that he has set forth for the country -- to get the economy moving and to focus on issues like health care, energy and education -- will now have a greater chance of moving forward."