During the first week of the August congressional recess Rep. Joe Sestak (D-PA) will kick off a major series of events tomorrow with what the campaign is calling a 'major announcement' tomorrow morning in Folsom, PA.

As first reported by TPMDC, Sestak began raising money for a Senate campaign in May, telling supporters at the time that he intended to challenge Sen. Arlen Specter (D-PA) in the Democratic Senate primary in Pennsylvania. Since then he's raised a significant amount of money, toured his entire state, and doubled down on his criticisms of his likely challenger. But he hasn't officially announced his candidacy. With an impressive haul in the second quarter, though--and with polls showing an appetite for a challenger in Pennsylvania--that could change tomorrow.

Sestak will also appear in Pittsburgh, Harrisburg, and Scranton, as well as on The Colbert Report as part of his campaign push this week.