"There may be better 100th-day presents to President Obama," said John Dickerson in Slate, "but they probably require witchcraft." Sen. Arlen Specter's decision to ditch the Republicans and become a Democrat will give his new party a filibuster-proof 60-seat majority, assuming Al Franken is seated as Minnesota's next senator. Now the question is whether Obama will return the favor and campaign for Specter in the primaries ahead of his tough 2010 re-election race.

The Democrats are happy now, said Doyle McManus in the Los Angeles Times, but they'll soon have days when they "wonder whether this was such a good deal." Specter will "be the 60th vote on every issue, just as he was on the stimulus bill -- the one who always has a special request before he can say yes."

Specter's surprise defection was a "crushing blow" to Republicans, said Fred Barnes in The Wall Street Journal, because it all but eliminated their ability to block liberal legislation. Now Republicans will have to win two or three Democratic seats next year to restore their ability to defeat legislation. "If they don't, the liberal heyday will go on."

This is a good day for Obama and a "wake-up call for Republicans," said John Avlon in The Daily Beast, but it's "a bad day for American centrists who believe in checks and balances." Specter's jump "undercut the already besieged centrist Republican tradition," and increased the power of right-wing activists. Nobody wins when the extremes in both parties take over.

That's the Democrats' problem now, said William Kristol in The Washington Post. Once they have a 60-seat majority, Obama will be "responsible for everything" and Democrats won't be able to complain about "GOP obstructionism" any more. "So, losing Specter may help produce greater GOP gains in November 2010, and a brighter Republican future."