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Facing a tough re-election fight in November, Rep. Ryan Costello, R-Pa., added his name on Sunday to a growing list of Republican incumbents bowing out of the midterm elections.

In an interview on MSNBC's "Kasie DC," Costello partly attributed his decision to a state Supreme Court ruling in January that found the Republican-drawn congressional map unconstitutional.

Costello, who was elected in 2014 in a district that includes suburban Philadelphia, also said his decision was motivated by intense opposition from the left and Republicans angered by his disagreements with President Donald Trump.

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"The combination of what I've had to deal with, just in terms of having a young family, [with] what the state Supreme Court did — which I think was obscene — along with the political environment has me led me to the decision," he told host Kasie Hunt. "It's been a very tough decision for me to make, but I think I'm making the right decision."

In a 4-3 decision, the Democratic-controlled court ruled in January that the Pennsylvania's congressional boundaries "clearly, plainly and palpably" violated the state's constitution.

Political observers have said the redrawn map — created by Stanford University Law Professor Nathaniel Persily — will likely help Democrats pick up seats in November.

In a statement, National Republican Congressional Committee Chairman Steve Stivers said Costello's retirement was a "great loss."

"We will work tirelessly to ensure this seat remains in Republican hands," Stivers said.