Liberal groups threaten centrists with primaries

Liberal groups announced today that they've raised millions of dollars to fund primary campaigns against any Democratic senator who joins Republicans in filibustering healthcare reform.

MoveOn and Democracy for America (DFA) told supporters in an email that they've raised over $3 million to support liberal primary challengers. (A DFA official says that number is now closer to $4 million.)

"It's up to us to be pro-active and stop a potential turncoat senator from killing President Obama's number one domestic priority," DFA said in the email.

"Today, we join MoveOn members, in pledging support for a primary challenge of any Senator in the Democratic Caucus who supports a Republican filibuster of a public option," the email continued.

The threat could be most immediately relevant to Sen. Blanche Lincoln (D-Ark.), who's facing a tough re-election in 2010 and hasn't seemed enthusiastic about a public option.

The only member of the Democratic caucus to suggest he'll actually join a filibuster is Joe Lieberman (I-Conn.). He's not up for re-election until 2012.