Rep. Joe Sestak (D-Pa.), who is challenging Sen. Arlen Specter (D-Pa.) in next year's Senate primary, is taking strongly to Twitter to promote the endorsement of Ned Lamont.

Campaigns usually tweet once about endorsements, but Lamont's backing may hold a special significance for Sestak. The congressman on Monday tweeted four times about Lamont; a tweet-up usually reserved for a special occasion, such as a presidential visit on the trail.

Lamont famously defeated centrist Sen. Joe Lieberman (I-Conn.) in the 2006 Senate primaries by pressuring him from the left. The former Democrat Lieberman beat Lamont in the general election as an independent.

Sestak is attempting a Lamont-like strategy against Specter, who left the Republican Party in April to become a Democrat. 

Here are Sestak's tweets, which include multiple photos:

Just finished the Stephanie Miller Show, now on the way to Independence Hall with Ned Lamont! #sestak

Sam Durso of Philly For Change introducing Ned Lamont #sestak #p2

Ned Lamont endorsing Joe Sestak For Senate and rallying support for change in 2010 #p2

Accepting the endorsement of Ned Lamont with Independence Hall as a backdrop. #sestak #p2

Sestak's campaign frequently uses the hashtag "#p2," which stands for "progressives 2.0" and is the primary topic indicator for liberal Twitter users.