WASHINGTON—In a stunning new blow to the Republican ultra-right, Sen. Arlen Specter (R-Penn.) announced today that he is switching from Republican to Democrat and will run for reelection in 2010 as a Democratic candidate for the U.S. Senate.

“Since my election in 1980,” Specter said in a statement, “the Republican Party has moved far to the right. Last year, more than 200,000 Republicans in Pennsylvania changed their registration to become Democrats. I now find my political philosophy more in line with Democrats than Republicans.”

His switch would give the Democrats the 60 vote margin they need in the Senate to break Republican filibusters, assuming that Democrat Al Franken of Minnesota is finally seated in the U.S. Senate. Franken’s GOP opponent, Norm Coleman, is appealing the ruling of a three-judge panel in Minnesota that Franken won in last November’s election.

Specter was one of only three Republican Senators who voted for President Obama’s $787 billion economic stimulus package last February.

But Specter recently announced he would not vote for the Employee Free Choice Act (EFCA), labor’s top priority, in its current form and said in the statement today he would not change his position nor be the automatic 60th vote.

However, Specter has enjoyed considerable labor movement support in past elections but he will not automatically receive that support running as a Democrat if he votes against EFCA.

Specter was facing a stiff challenge in the Republican primary from Rep. Pat Toomey, a right-wing extremist backed by the “Club for Growth.”

The rabid ultra-right was oozing venom from every pore over Specter’s announcement. The Human Events blog carried blog entries snarling at Specter as a “RINO” (Republican in name only), a “rat” and “miscreant.”

But for the grassroots movements of the people fighting to push through EFCA, Obama’s $3.5 trillion budget and other programs, the announcement was warmly welcomed.