Rep. Roscoe Bartlett drew his most significant primary challenger yet Thursday, when Maryland Republican Party Chairman Alex X. Mooney announced that he would form an exploratory committee to run for Bartlett’s seat.

Bartlett’s fate has been uncertain since the state’s new redistricting map pushed his 6th Congressional District down into Democratic-leaning Montgomery County. Bartlett has vowed to run for an 11th term but the seat has been laced with intrigue this week amid reports that Bartlett’s chief of staff, Bud Otis, has been soliciting support for a congressional bid of his own in case Bartlett decides not to run.

Mooney, a former state senator from Frederick who worked on Bartlett’s staff for a short period in the early 1990s, had been mulling whether to enter the race himself for months, and the news of Otis’s maneuvering appears to have pushed him into a decision.

“With the recent news about Congressman Roscoe Bartlett’s long time chief-of-staff preparing to run for Congress and the Democratic Party’s cynical and corrupt redistricting plan to oust Congressman Bartlett, I felt it was time for me also to start an exploratory committee for Congress,” Mooney said in a statement released Thursday morning.

The statement adds that Mooney plans to officially file as a candidate in January, at which point he will step down from his post with the state party.

In November, Mooney lost his race for a fourth term in the state Senate. He was elected state party chairman in December, and speculation quickly turned to whether he would decide to make a run for Congress.

Five Republicans, including Bartlett, have filed to run in the 6th District. State Sen. David Brinkley (R-Frederick) and state Sen. Christopher Shank (R-Washington County) are also considering bids.