Democrat Joe Sestak came tantalizingly close to winning a U.S. Senate seat in Pennsylvania in 2010, and is hoping Tuesday to secure a rematch.
But the party establishment wants nothing to do with him and has poured millions into the campaign of his chief primary rival, Katie McGinty.
McGinty is a former state and federal environmental policy official who has worked for Al Gore, Bill Clinton, Gov. Tom Wolf and former Gov. Ed Rendell.
Sestak is a former two-term congressman and retired Navy rear admiral.
They are looking to take on Republican Sen. Pat Toomey this fall in a race that could tilt control of the Senate.
The bad blood between Sestak and the party dates to 2009, when the Democrats recruited him to run for Senate, then asked him to step aside. He refused.