A poll out Tuesday morning shows Democrat Conor Lamb with a double-digit lead over Republican Keith Rothfus in Pennsylvania’s closely watched 17th Congressional District.

The race marks the only battle between two Congressional incumbents this election cycle. If the results hold up, it means Lamb, who won a special election to represent the 18th District in March, will have won two hotly contested Congressional races in less than eight months.

The survey, from New Jersey’s Monmouth University, shows Lamb, of Mt. Lebanon, leading Sewickley's Rothfus by 51 to 39 percent among potential voters, with 9 percent of voters undecided. And while Monmouth made projections for a few different turnout scenarios, Lamb held that lead in all of them. If voters turn out at rates typical for a midterm election, Monmouth projects a 53-to-40 lead for Lamb. A “surge” model which projects heavy Democratic turnout gives a statistically similar 54-to-39 percent lead.

All those leads are outside the poll’s margin of error.

“The Democratic lean of the [17th] gives Lamb a decided advantage, with many voters expressing doubts about economic policies put forth by both the White House and the GOP Congress,” the release accompanying the poll says.

The 17th District was drawn by the state Supreme Court earlier this year. The new district -- which includes all of Beaver County and suburban areas of Allegheny -- is more competitive for Democrats than the district Rothfus currently represents.

Rothfus beat Democrat Mark Critz in 2012 in what was then the 12th District: Donald Trump won the 12th by 20 points in 2016. But the new district – which jettisons rural, Republican parts of the 12th and replaces them with more Democrat-friendly suburbs – went for Trump by just 2 percentage points.

In an interview, Monmouth pollster Patrick Murray said that for Rothfus, "This is live by the sword, die by the sword. Rothfus came into office because of a gerrymandered map [drawn to help Republicans]. And now the new map may really be the death knell for him."

Murray said that of the seven battleground races Monmouth has polled so far this year, "This is the one where the Democrat has the biggest advantage."

Lamb won a special election in March, besting state Rep. Rick Saccone in the current 18th District. Portions of that district in the South Hills have been included in the 17th, and Lamb appears to still be enjoying a honeymoon: 44 percent of voters say they have a “favorable” view of him, while only 17 percent see him unfavorably. Rothfus, by contrast, is seen favorably by 31 percent of voters, while 23 percent see him unfavorably.

Notably, more voters reported having “no opinion” on Rothfus than Lamb: 46 percent of voters said they had no opinion on his performance, compared to 39 percent for Lamb. That's despite the fact that Rothfus is a three-term legislators, while Lamb is a newcomer that Western Pennsylvania voters were all but completely unaware of until late last year.

"In the other races we've polled, if there's an incubment in the race, they are generally well known," Murray said.

Lamb's name recognition, meanwhile, is high after the special election, which saturated local airwaves with ads for and against him. And the new district includes some suburban areas that were previously lumped in with the city of Pittsburgh, where Democrat Michael Doyle has long held sway. Murray surmised that would inspire some voters becuase "For many Democrats, this is the first time they can vote and have it mean something" in a House race.

"Conor Lamb's heightened profile, the addition of Pittsburgh suburbs to the district, and the overall national political trends -- you put that all together and it's a good picture for Democrats."

Indeed, political handicapper Dave Wasserman this week called Rothfus one of the country's two most vulnerable Republican incumbents. And his employer, the Cook Political Report, shifted its assessment of the district from "toss up" to "leans Democratic" the same day the Monmouth poll was released.

Trump’s own favorability ratings may also play a part. While district perspectives on him are mixed – 44 percent approve of his job performance while 51 percent disapprove – he appears to be producing an “enthusiasm gap” that may help Lamb.

Voters are evenly divided on which party should control Congress. But Democrats are more likely to report having a high level of interest in the race. Some 43 percent of District 17 voters say they strongly disapprove of Trump job performance, compared to only 28 percent who strongly approve – a reflection of how Trump has mobilized opposition since his election.

Signature GOP policies don’t appear likely to help Rothfus much. The GOP’s landmark 2017 tax bill may be slightly more popular than not – 43 percent approve to 39 percent disapprove. But more than two-thirds of voters expect their tax bills to go up or remain the same as a result of it. Nearly half of voters say Trump’s trade policies will hurt the local economy – fewer than one-third believe it will help.

Monmouth polled 401 voters in the district between July 19 and July 22, with live phone calls to both cell phones and landlines. The outfit last checked in on Lamb’s prospects one day before Lamb’s March 13 special election win: It projected Lamb winning by from 2 to 7 points, depending on the turnout model used. Lamb ended up winning that race by less than one-half of 1 percent.

Republicans sought to beat Lamb this spring by citing his opposition to the tax cuts and linking him to Nancy Pelosi, the controversial leader of House Democrats – even though Lamb said he would prefer to replace her as leader. Republicans have already cribbed pages from that playbook in this race – Vice President Mike Pence faulted Lamb on taxes and Pelosi during a fundraising stop in Moon last month.

It remains to be seen whether the strategy works better this time. Monmouth found voters slightly more likely to complain of Rothfus’ support of Trump than of Lamb’s ties to Pelosi.

“Lamb made a point of distancing himself from Pelosi … last March,” Murray said in the statement. “It will probably be easier for him to maintain that distance than it will be for Rothfus with Trump."