A scandal-plagued incumbent senator running against an independently wealthy Republican has made a reliably blue state into a battleground that Democrats suddenly need to defend.

The Senate map was always going to be tough for Democrats. No matter how favorable the political climate, Democrats knew they would struggle to retain seats in deep-red states such as Indiana, West Virginia and North Dakota.

But New Jersey?

In recent weeks, national Democrats have poured millions into the race to save Sen. Robert Menendez as public polls have shown the senator ahead but only a hair outside the margin of error. Late last week, the Cook Political Report moved the race to a “toss-up."

A Republican hasn’t won a U.S. Senate seat in Jersey in 46 years. President Trump lost the state to Hillary Clinton by 14 points. Compare that to neighboring Pennsylvania, which Trump won, where incumbent Democratic Sen. Bob Casey is expected to win easily by double digits.

But Menendez, who is seeking a third term, has struggled to shed his considerable baggage. For those who need a quick primer: Menendez was indicted in 2015 on charges that he helped a top campaign contributor and friend, who took Menendez on lavish trips on his private jet, skirt government regulations. The case went to trial in Septemer 2017. Two months later, the jury was deadlocked and a mistrial was declared. The Senate Ethics Committee took up the case in January 2018 after the judge acquitted him on the most serious charges. In April, the Senate committee found Menendez guilty of breaking federal law, formally admonished him and ordered that he pay back all the gifts he received.

In addition, campaign ads resurrected the allegation that Menendez slept with underage prostitutes in the Dominican Republic, which, despite FBI and media investigations, was never proven to be true.

Jersey voters have a strong stomach for scandal, and state Democratic leaders have stayed loyal to Menendez. Yet this race is way closer than it should be.

Meanwhile, the New Jersey Star-Ledger editorial board told voters Monday to “choke it down, and vote for Menendez.” The board acknowledged Menendez’s flaws, wrote that he should have stepped aside to make way for a less embattled Democratic candidate, and then made the case that he is still better than the alternative — pharmaceutical CEO Bob Hugin,.

The Wall Street Journal editorial board jumped all over that argument and called Democrats hypocrites for putting pressure last year on Alabama Republicans to oppose Roy Moore, the Senate candidate accused of dating and pursuing teenage girls when he was in his 30s, while urging Jersey Democrats to support Menendez despite his Senate admonishment and questionable ethics.

“Rank-and-file Democrats can show they’re a moral match for Alabama Republicans if they decide to vote for Mr. Hugin or stay home. Otherwise, spare us the lectures about the moral consequences of Donald Trump,” the WSJ editorial board wrote.

It’s hard to imagine a scenario in which many of the state’s Democrats vote for Hugin, so the real question is whether the lackluster ticket will suppress voter turnout enough that Republicans can eke out a win.

While Menendez is likely to still survive given Democrats' primary motivation to provide a check on President Trump, it’s not unheard of for politicians with a scandal hanging over them to lose their seat in a year favorable to their party.

In 2002, when Republicans gained seats after the 9/11 attacks, incumbent GOP Sen. Tim Hutchinson lost his reelection to a Democrat in conservative Arkansas after leaving his wife for a much younger staffer.

(Correction: An earlier version said a judge dismissed charges. Menendez was actually acquitted of the most serious charges.)