Republican Rep. Leonard Lance is struggling in his bid for re-election in a wealthy Central Jersey suburban district that is one of the nation's top congressional battlegrounds, a Monmouth University poll released Thursday said.

And President Donald Trump and the GOP tax law are weighing him down.

A five-term incumbent from Clinton Township, Lance trailed Democratic challenger Tom Malinowski of Rocky Hill 47 percent to 39 percent, with 12 percent undecided, among all potential voters, a group defined as those who voted since 2010 or registered since then, the poll found.

Using a turnout model that is typical for midterm elections, Monmouth measured Malinowski's lead as 46 percent to 43 percent. Using a model that anticipates a surge in turnout in Democratic areas, Malinowski's lead grew to 47 percent to 41 percent. Both of those results were within the poll's 7.2-percentage-point margin of error for the spread between the candidates, meaning they are not statistically significant.

Lance is the most vulnerable Republican incumbent running in New Jersey, as Democrats look to Garden State voters to help them pick up as many as four of the 23 seats needed to win control of the House this November.

Lance is helped by his deep roots in the district, which include serving in the state legislature from 1991 until he took his seat in Congress in 2009, pollster Patrick Murray said.

But Murray said Trump's unpopularity is the lowest Monmouth found in polling 12 bellwether districts around the country, with 39 percent approving of Trump and 55 percent disapproving. Within those figures, 47 percent strongly disapprove, while just 26 percent strongly approve.

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Asked if they support or oppose what Trump is doing on most issues, 37 percent said support and 53 percent said oppose. Asked which party voters would rather see control Congress, 46 percent said Democrats and 32 percent said Republicans.

Lance spokesman Jim Hilk pointed to a "live poll" underway on The New York Times' website that on Thursday had him leading, 48 percent to 44 percent. Hilk also said the campaign's internal polls also had him ahead.

"The Monmouth poll is an outlier when it comes to the state of the race," Hilk said.

Campaign manager Colston Reid said Malinowski was taking nothing for granted.

"If you want to change Congress, you have to change your congressman, and we're going to fight every minute of every day to make sure that happens," Reid said.

The 7th District Lance represents reaches from Hunterdon County on the Delaware River to Union County, and is home to Bedminster, where Trump owns a golf course and has spent many weekends and vacations. The district backed Republican Mitt Romney for president by 6 percentage points in 2012, but gave Hillary Clinton a 1 percentage point win over Trump in 2016. Lance won those elections by 17 points and 11 points, respectively.

The poll found Lance leads among white voters without a college degree 50 percent to 36 percent, but Malinowski leads among college-educated white voters 50 percent to 39 percent and among all non-white voters 64 percent to 20 percent.

The tax law, which Lance opposed largely because it imposed a $10,000 cap on the deduction for state and local taxes, is supported by 34 percent of voters, while 49 percent disapprove. Just 20 percent of voters in the district said they think their taxes would go down.

"It's hard to buck a trend where voters really dislike both your party's leader and signature accomplishment," Murray said. "But Lance is keeping this race close on the back of his reputation as a moderate as well as the goodwill he has built with constituents while in office. It remains to be seen whether this will be enough to hang onto the seat."

The poll found 35 percent of voters have a favorable impression of Lance, while 21 percent have an unfavorable one, and 44 percent have no opinion. For Malinowski, those figures were 26 percent favorable, 14 percent unfavorable and 60 percent no opinion.

Lance's campaign has touted his record for bipartisanship, and the Lugar Center at Georgetown University ranked him 13th among all House members in that area. He also serves with Rep. Josh Gottheimer, D-Wyckoff, on the House Problem Solvers Caucus, which works to craft bipartisan agreement in a chamber better known for battles between the right and the far right.

Malinowski is a former assistant secretary of state in President Barack Obama's administration, and served as Washington director for Human Rights Watch. His fundraising far surpassed Lance's, and on June 30 he had $1.6 million in his account compared with Lance's $1.2 million.

Super PACs that can take unlimited contributions have also been funding attack ads in the district, with the Republican-backing Congressional Leadership Fund spending $1.6 million already while the Democratic House Majority PAC spent $667,000.

The Monmouth poll was conducted by phone from Sept. 13 to Monday and surveyed 414 voters in the 7th District. Responses to individual questions have a margin of error of plus or minus 4.8 percentage points for the full survey and 5.1 points for the likely voter models. The error for the gap between candidates is plus or minus 6.7 points for the full sample and 7.2 points for the likely voter models.

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