Republican-turned-Democrat U.S. Sen. Arlen Specter will likely face a formal challenge in Pennsylvania's Democratic primary.
U.S. Rep. Joe Sestak, from Delaware County, a former Navy vice admiral serving his second term in Congress, has scheduled five campaign stops throughout the state today.
At the first, at a VFW hall in his district in Folsom, he's expected to announce his candidacy.
The announcement would not be a surprise.
Sestak, 57, has already heavily campaigned in the state.
The five-term Specter severed his decades-long ties to the Republican Party in April.
He said, in part, it was to avoid a primary challenge from former Rep. Pat Toomey, who nearly beat him in the 2004 primary.