Republican Rep. Ryan Costello plans to drop his bid for reelection in the 2018 House election for Pennsylvania's 6th Congressional District and will retire at the end of his term, a Republican familiar with Costello's plans told CNN Saturday.
"It's going to happen," a Republican familiar with Costello's plans told CNN without sharing details about the timing.
A spokesman for Costello did not immediately respond to CNN's request for comment.
City&State PA previously reported on Costello's plans.
Pennsylvania's Supreme Court recently ruled that the state's congressional districts were gerrymandered and put a new map in place for November's midterm elections. Earlier this week, the US Supreme Court denied a request from Pennsylvania Republicans to block new congressional maps.
A two-term congressman, Costello won his previous races in a then-more favorable district for Republicans with 57% of the vote in 2016 and 56% in 2014.
The new map, however, favors Democrats in the redrawn district, which encompasses Chester County and the largely Democratic city of Reading, and will be tough for Republicans to hold.
Since 1994, a president's party has never been successful in keeping open seats in midterm elections that were carried by the other party in prior presidential elections. Hillary Clinton beat President Donald Trump by 10 percentage points in Chester County in the 2016 presidential election.
Costello's decision to retire comes on the heels of Democrat Conor Lamb's defeat of his Republican opponent, Rick Saccone, in a close race in the special election for Pennsylvania's 18th district, which Trump carried in 2016 by 20 percentage points.
With Costello bowing out, there is currently one other candidate, Greg McCauley, a local tax attorney, seeking the Republican nomination, while Chrissy Houlahan, an Air Force veteran, former teacher and former business and nonprofit executive, is the lone Democrat in the 6th Congressional District race.
Costello is the 39th Republican lawmakers to announce his retirement from Congress.