Democrats may have a primary to deal with as they seek to win retiring Rep. Jim GerlachJames (Jim) GerlachPa. GOP 'disappointed' by rep retiring after filing deadline Pennsylvania Republican Costello won't seek reelection Republican Pa. congressman won't seek reelection: report MORE's (R-Pa.) seat, according to

Former Democratic nominee Manan Trivedi will announce a third bid for the seat on Tuesday, the website reports.

That sets up a primary between Trivedi, a Marine veteran who lost to Gerlach by double-digit margins in both 2010 and 2012, and Army veteran Mike Parrish (D).

National Democrats have been quietly supporting Parrish in the race, seeing him as their best chance of winning the slightly Republican-leaning district ahead following Gerlach's retirement. But Trivedi might give him problems in the primary: Parrish recently switched parties and has donated to a number of Republican candidates over the years, and Trivedi won a contested 2010 primary by running to his opponent's left.

Republicans also may have a contested primary. The exurban Philadelphia seat is a top Democratic target.