Sen. Bob Menendez’s (D-NJ) seat — normally considered safely in a Democratic stronghold — is now a toss-up, according to the latest ratings from the nonpartisan Cook Political Report.

The race between longtime incumbent Menendez and Republican Bob Hugin appears to be narrowing with Menedez’s recent corruption trial on voters’ minds. The corruption trial happened about a year ago, and ended in with a hung jury and a mistrial.

“The biggest threat to Menendez’s re-election is not so much Hugin than it is the voter who goes to the polls and decides to send Menendez a message, much the way many did in the primary when 38 percent voted for his unknown primary opponent,” wrote Cook Political Report’s Senate editor Jennifer Duffy in the latest ratings. “There is certainly a thumb on the scale for Menendez, who is said to have a lead of between four and six points, in this very blue state, but the race is close enough to warrant a move to Toss Up.”

Menendez still leads every poll, and is up by about 7 points, per the latest RealClearPolitics average. But recent polls also show his support among independent voters is eroding. The situation in New Jersey presents a larger problem for Senate Democrats. There is a nightmare scenario where they hold all their tough red states; pick off an important swing state like Nevada, Arizona, or Tennessee; and still fail to take back the Senate when it all comes crumbling down in New Jersey.

As Democrats ramp up an anti-corruption message in 2018 aimed at stamping out lobbying and money in politics, Hugin has spent the summer attacking him as corrupt.

“The corruption factor is just a cloud over this entire race,” said Carl Golden, a former spokesperson for past New Jersey Govs. Chris Christine, Todd Whitman, and Thomas Kean, and longtime political analyst.

Menendez’s seat is certainly far from the closest Senate race on the ballot this fall, but it’s a problem for Senate Democrats in a year in which they need everything to go just right.

“There’s no question in anybody’s mind in New Jersey that this race is much tighter than it should be,” said Patrick Murray, polling director at Monmouth University. “If you had a clean Democratic candidate running here, they should be ahead by 20 points.”

Recent polling shows the race narrowing

Menendez’s seat has always been easy for Democrats to hold onto; there are almost double the number of registered Democrats as Republicans in New Jersey, and the state hasn’t sent a Republican to the Senate since the early 1970s.

But dismal approval numbers and a number of recent single-digit polls have Democrats worried they could lose a Senate seat they’ve had on lockdown for decades. Stockton University released a poll last month showing Menendez ahead of Republican challenger Bob Hugin by just 2 points — a statistical dead heat. “It feels like a lot of momentum with Hugin,” John Froonjian, senior research associate at Stockton University’s William J Hughes Center, told Vox at the time.

Both Murray and Duffy said the poll had major problems, including undersampling minority and young voters.

“It’s not that this poll might be off, but if it’s accurate, it’s not because of sound methodology,” Murray said.

But recent polls have shown the race tightening. An October 17 Quinnipiac University poll of registered voters showed Menendez ahead of Hugin by 7 points, while a Rutgers University poll released Wednesday showed the incumbent ahead by 5 points. A Monmouth University poll released last week had Menendez ahead by 9 points among likely voters.

“I don’t believe [the Stockton] poll,” said Duffy. “I don’t think it’s that close. Do I think Hugin has done some damage to Menendez? Yes.”

Democrats are running on anti-corruption, and Menendez is a sore point

As Vox’s Andrew Prokop has detailed, in April 2015 the Justice Department brought a corruption case against Menendez, who it accused of using his position as a senator to benefit a Florida eye doctor named Salomon Melgen — someone convicted of defrauding Medicare of more than $90 million. Menendez calls Melgen a friend, but vehemently denies committing crimes to help him.

As Prokop wrote last year:

Prosecutors are alleging that Menendez accepted expensive gifts from a wealthy supporter and friend, Dr. Salomon Melgen, in exchange for intervening on behalf of the doctor’s business interests with government officials (and trying to get visas for the doctor’s girlfriends). Menendez asserts he’s done nothing wrong.

The case was closely watched in 2017; New Jersey still had a Republican governor during part of the trial, and Democrats feared Menendez could be expelled from the Senate and replaced with a Republican if he was convicted. But the jury deadlocked, unable to reach a conclusion.

Now Menendez is running for reelection in a year that coincides with national Democrats running on an anti-corruption message about cleaning up Washington.

Golden, a longtime political insider in New Jersey, says he’s not aware of any conversations Democrats had asking Menendez to step aside leading up to the race. But there is real anxiety within the state party about his chances, Golden added.

“I know there have been some internal conversations and real nervousness about it,” he said. “I do know there have been conversations within the party ... we hadn’t counted on this, we’re looking at keeping our congressional seats.”

Menendez’s reelection bid received a jolt during the summer primary, when a little-known Democratic candidate named Lisa McCormick who didn’t spend on her race still received 40 percent of the vote.

While Menendez wasn’t convicted and continues to maintain his innocence, it appears New Jersey voters aren’t as convinced. An August Quinnipiac poll showed a large number of New Jersey voters, 49 percent, said they believed Menendez was involved in serious wrongdoing. Sixteen percent who said they didn’t believe it. And 47 percent of voters said they disapproved of his performance in office, while 40 percent approved.

That’s been a persistent issue for Menendez, the majority of likely voters told pollsters they don’t think he is honest. The candidate needs to count on the support of women voters who want to send a message to Trump and Republicans, according to pollsters.

“Support from women remains key to Sen. Robert Menendez’ standing in this race as his favorability rating is stuck deep underwater,” said Quinnipiac polling analyst Mary Snow in a statement. “The question for Bob Hugin is: can he win over those voters who say they are undecided or are backing Menendez and indicate they may change their mind?”

Menendez’s Republican opponent Hugin has seized on the Democrat’s trial, spending millions on ads slamming the senator as corrupt. And it’s appearing to be an effective message.

“People are looking at that trial and saying ‘he really wasn’t acquitted,’” Golden said. “There’s still a real question about his guilt, you can see that underlies a lot of it. People think that what he did was incredibly improper, criminal at least in the eyes of the Justice Department a year or so ago. That’s some extremely heavy baggage to run with.”

How much trouble is Menendez really in?

How worried should Democrats be about losing a Senate seat in New Jersey? In the first place, they haven’t had to contend with a such a close race in a long time.

Menendez’s big problem seems to be that Democrats so far are saying they are undecided about who to vote for, or whether to vote in November.

And (as Republicans have gleefully noted), Democrats are spending a lot on the race — dumping resources into a normally safe Senate seat as they also try to defend tougher seats.

Senate Majority PAC has spent about $6 million on the race so far, recently putting down another $3 million in television ad buys to boost Menendez. And the Democratic Senate Campaign Committee (DSCC) dropped $117,000 on an ad buy supporting Menendez that ran from late August to early September, and spent another $340,000 for more ad buys in late August, per the North Jersey Record.

The DSCC didn’t spend any money on Menendez in 2012, the last year he ran. Golden thinks Democrats will have to spend a lot on get-out-the vote efforts this year, something they haven’t had to do much of before.

“They have to spend a hell of a lot of money to get their people out to the polls,” he said. “I don’t think the national Democrats anticipated having to put any money into the New Jersey Senate race.”

Of course, Golden, Murray, and others in New Jersey caution not to count Menendez out. He’s a well-known political entity in the Garden State, and will be spending plenty of money attacking Hugin’s pharmaceutical background and campaign contributions to President Donald Trump, who is supremely disliked in the Garden State.

“We have enough voters saying I’m willing to hold my nose and vote for Menendez,” Murray said.