Rep. Conor Lamb (D-Pa.) has a 12-point lead over opponent Rep. Keith Rothfus (R-Pa.) in the nation's only incumbent-versus-incumbent contest of the midterms.

Lamb and Rothfus are running in Pennsylvania's newly-drawn 17th District.

The Pennsylvania Supreme Court ruled in January that the state's congressional map is the result of gerrymandering to the point that it violates the state constitution. It ordered the map be redrawn before the midterm elections.

Lamb gets the support of about 54 percent of likely voters in the district, while 42 percent support Rothfus, according to a new Monmouth University poll released Wednesday. Lamb's margin is similar to the 13-point margin from Monmouth University's July poll.

Lamb made national headlines in March when he won a special election to represent Pennsylvania's 18th Congressional District in a tight race decided by fewer than a thousand votes.

While the 18th Congressional District was long held by GOP Rep. Tim Murphy, the newly drawn 17th Congressional District is much more amenable to Democrats. The poll found that 54 percent of voters identify as Democrats, 34 percent as Republicans and 7 percent as neither.

Republicans had last drawn the map in 2011.

While both candidates have net-positive favorability ratings, Lamb's margin is far higher than Rothfus's. Likely voters view Lamb favorably by a 52 percent to 20 percent margin, with 27 percent undecided, while they find Rothfus favorable by a 37 percent to 32 percent margin, with 31 percent undecided.

President Trump's underwater approval rating is a possible anchor on Rothfus. About 41 percent of likely voters polled approved of the job Trump is doing, while 58 percent disapproved.

About 73 percent of voters polled said the president plays an important role in their vote, yet this motivation is more common among Trump opponents (83 percent) than Trump supporters (66 percent).

Trump endorsed Rothfus, tweeting last month, "Congressman Keith Rothfus continues to do a great job for the people of Pennsylvania. Keith is strong on Crime, the Border, and our Second Amendment. Loves our Military and our Vets. He has my total Endorsement!"

However, only about a third of likely PA-17 voters have heard about the president's endorsement.

"It's probably good news for Rothfus that few voters are aware of Trump's endorsement because it really doesn't help him," Patrick Murray, director of the independent Monmouth University Polling Institute, said in a press release from the university.

Monmouth University surveyed 354 likely voters from Oct. 5-8. The poll has a margin of error of +/- 5.2 percentage point.