Chris Brennan breaks the news that Joe Khan, a former federal prosecutor who recently left the U.S. Attorney's office, will challenge Seth Williams in the Democratic primary for District Attorney in 2017.

Khan will officially announce his candidacy later today, and Brennan reports his campaign will focus on Seth Williams's ethical blunders:

Central to Khan's candidacy is restoring integrity to the District Attorney's Office, which has been buffeted with criticism as federal investigators probe Williams' personal, political, and nonprofit finances.

"He was someone who actually had some good ideas," Khan said of Williams. "That person who came into office seven years ago is a very different person today. He has really lost his way."

Khan prosecuted the political corruption cases in Allentown and Reading along with the 'Match.com rapist' case. An unscientific poll on PoliticsPA recently found him leading the pack among that blog's political insider readers.

Attorney and former Nutter managing director Rich Negrin has been expected to enter the race, and cookie magnate Joe Untermeyer of Famous 4th Street Cookie Co. had a poll in the field recently. 

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