Pennsylvania Rep. Conor Lamb (D) holds a double-digit advantage over his GOP opponent and fellow congressman in the newly-drawn 17th Congressional District, according to a poll released Tuesday.

A Monmouth University poll found Lamb, a freshman lawmaker who defeated Republican Rick Saccone in a special election earlier this year, holds a 12-point lead over fellow Rep. Keith Rothfus Keith James RothfusCNN's Tapper tried to talk GOP candidate out of running against Democratic incumbent: report Lobbying world Conor Lamb gets 2020 challenger touted by Trump MORE (R-Pa.).

Rothfus was first elected to office in 2013. Pennsylvania's 17th District has been labelled "lean Democratic" by The Cook Political Report.

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Lamb enjoys the support of just over half of the potential voters who were polled, 51 percent, while Rothfus lags behind at 39 percent, according to the Monmouth poll. A historical midterm model used by the poll predicts Lamb's eventual share of the vote at 53 percent to Rothfus's 40 percent.

A secondary model predicting the results of an election with a surge in Democratic turnout put Lamb slightly higher, at 54 percent to Rothfus's 39 percent.

Lamb also holds higher favorability ratings in the poll, with 44 percent of respondents supporting his job performance so far compared to just 31 percent for Rothfus.

One contributing factor noted by the pollsters is President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE's approval rating, which is underwater in the district. Just 44 percent of voters in the district support the job Trump is doing in office, according to Monmouth, while 51 percent disapprove.

A positive sign for Rothfus in the poll was support for the Republican tax-reform plan passed last year, which remains popular with 43 percent of voters who took the poll, while 39 percent of them are opposed to the changes.

Still, voters surveyed were more likely to say that their personal tax bill would increase (31 percent) rather than drop (22 percent) because of the law. Most voters, 38 percent, said that they didn't expect any changes to their tax bill.

Monmouth University's poll, conducted July 19-22, contacted 401 voters who have participated in some way since 2010 in Pennsylvania’s 17th District. The poll's margin of error is +/- 4.9 percentage points.