Democrats might have more work to do than usual in New Jersey.

Sen. Bob Menendez's lead in his re-election bid over Republican challenger Bob Hugin has dwindled with his favorability rating underwater, according to a Quinnipiac University poll released Wednesday. Forty-three percent of voters back the incumbent Democrat, while 37 percent support the GOP former pharmaceutical executive, the survey said.

Another poll released by the university in March — before the state held primary elections or Menendez was "severely admonished" by the Senate's ethics panel for his behavior in office — found a 17 percentage point edge for the Democrat.

The poll result shows Democrats may have to labor to keep a Senate seat in a state that a Republican has not represented in the chamber since the early 1980s. The party hardly needs a competitive race in a traditional stronghold, as Democrats and independents who caucus with them defend 26 Senate seats this year. Ten of those are in states President Donald Trump won in 2016.

Though the race appears much closer than Democrats would want it, the state's partisan leanings still favor Menendez. A midterm year marked by Democratic enthusiasm could also help the senator avoid an upset.

Hugin, the former CEO of drugmaker Celgene, has used his personal wealth to fund a barrage of television ads in the state branding himself as an independent voice and characterizing Menendez as corrupt. The Republican had given more than $15 million to his campaign as of June 30, and it had already spent $8.6 million. It had $8.1 million in cash on hand at the time.

Earlier this year, prosecutors acquitted Menendez, who faced allegations that he gave political favors to a wealthy Florida eye doctor in exchange for gifts. But the Democrat did face admonishment from his colleagues in April.

Menendez's campaign has one advantage. It started its multi-million dollar ad campaign only this week. The Democrat's campaign had spent about $3.9 million as of June 30, less than half of what Hugin's campaign had shelled out. It had about $6.4 million in cash at that time.

In a TV ad released Wednesday, Menendez accused Hugin of lining his pockets "to the tune of millions by gouging cancer patients." Hugin has said he is proud of his record of job creation at Celgene, and argued that it "created value" by putting nearly 40 percent of its revenue back into research and development of new products.

Wednesday's Quinnipiac poll shows some potential trouble spots for both candidates. Only 29 percent of voters said they had a favorable opinion of Menendez, versus 47 percent who responded that they have an unfavorable view.

In addition, about 49 percent said they believe he was involved in serious wrongdoing. Only 16 percent answered that they do not think so, while 31 percent said they had not heard enough to make a judgment.

Forty percent of voters said they approve of the job Menendez is doing as senator, while 47 percent responded that they disapprove.

The poll also suggests that Hugin still has issues getting his name out, despite his spending on ads. While the former executive had a positive favorability rating in the Quinnipiac survey, more than half of respondents said they hadn't heard enough about him to know whether they like him.

In a statement, Hugin communications director Megan Piwowar contended that the poll shows Menendez "is running scared and he should be."

Conversely, Menendez campaign communications director Steven Sandberg argued that the survey shows "how resilient and strong the support is" for Menendez despite Hugin's heavy ad spending.