WEST CHESTER, Pa. (AP) — A Republican Pennsylvania congressman has announced that he will not seek re-election, boosting Democratic hopes of winning his House seat.

U.S. Rep. Ryan Costello announced on Sunday that he would not be running, ending weeks of speculation about his future.

- Advertisement -

During an appearance on MSNBC, the second-term congressman called it “the most difficult decision” he’s ever had to make and said it was due to a number of factors including the state’s new congressional map.

Under the discarded map, Costello’s suburban Philadelphia district had a Republican majority that nevertheless helped Clinton beat Trump there by 2 percentage points in 2016. The redrawn district has slightly more Democrats and Clinton would have won it by 9 percentage points.

Costello was expected to face a tough election battle against Democrat Chrissy Houlahan.