The Pennsylvania Democratic Party on Saturday endorsed Sen. Arlen Specter's reelection bid over primary challenger Rep. Joe Sestak. 

The incumbent senator, who switched parties last year in part to win reelection, tweeted Saturday:

Thank you to the Pennsylvania Democratic party for your endorsement and support.

Looking forward to working with you to achieve Democratic victory in 2010.

Specter holds wide leads over Sestak in the polls, but Republican nominee former Rep. Pat Toomey (R) leads both in the polls. The nonpartisan Cook Political Report rates the race as a toss-up.

Sestak had attempted to outflank Specter on the left, but Specter has repeatedly gone after Sestak's missed votes in the House and has used his experience and name recognition to open a wide lead in the primary.