April 28 (Bloomberg) -- Pennsylvania Senator Arlen Specter, a stubbornly independent lawmaker who has long bucked the Republican Party, announced he will seek re-election as a Democrat because his former party has “moved far to the right.”

The addition of Specter to the Democratic caucus, if combined with the seating of Al Franken in Minnesota’s disputed Senate race, would give the party the 60 votes required to break filibusters that can stall legislation in the Senate.

Specter, though, told a packed news conference in Washington that, “If the Democratic Party asks too much, I will not hesitate to disagree and vote my independent thought.” The 79-year-old lawmaker said he is full of “vim, vigor and vitality.”

Specter and two other Republican senators voted for President Barack Obama’s $787 billion economic stimulus measure, fueling opposition from party voters in Pennsylvania. Polls showed he faced an uphill primary fight to win renomination as a Republican for the Senate next year.

“My change in party affiliation does not mean that I will be a party-line voter any more for the Democrats than I have been for the Republicans,” Specter said a written statement earlier today.

A 60-vote Democratic majority would block a Republican “reversion to knee-jerk filibuster,” said New York Democrat Charles Schumer. “There will be much more debate, much more progress.”

To contact the reporters on this story: James Rowley in Washington at jarowley@bloomberg.net; Christopher Stern in Washington cstern3@bloomberg.net

Last Updated: April 28, 2009 14:42 EDT