Republican Corey A. Stewart, left, and Democratic Sen. Tim Kaine talk after a Virginia senatorial debate on Wednesday in McLean. (Katherine Frey/The Washington Post)

IT’S ALWAYS hard to know when Corey A. Stewart, the race-baiting, bottom-feeding Republican candidate for Senate in Virginia, has hit a new low, given his formidable capacity to delve ever more deeply into the political depths. Still, he proved his mettle, and, as he intended, made headlines with a deep dive into character assassination by insinuating — without a gossamer’s wisp of evidence — that the state’s Democratic incumbent, Sen. Tim Kaine, had been accused of sexual harassment.

Mr. Kaine has never been thusly accused; in fact, he is known for his decency and probity. But facts are beside the point for Mr. Stewart, whose meager campaign budget is as depleted as his reputation, prompting him to grab attention any way he can.

When, during their prime-time debate Wednesday, Mr. Kaine pointed out, accurately, that there have been no sexual complaints against him, Mr. Stewart replied, with McCarthyite aplomb, “How do we know that?”

We know it the same way we know that Mr. Stewart has been an embarrassment to Virginia, to the Republican Party and to suburban Prince William County, whose board of supervisors he chairs: We can look it up.

Mr. Stewart trails his opponent badly in the polls in this, his first statewide general-election campaign, for excellent reasons. In Virginia, a centrist state known until recently for the relative restraint of its partisan rhetoric, he has set new standards for venomous innuendo, race-tinged provocation and divisiveness.

He entered this contest pledging to wage a “vicious” campaign against Mr. Kaine. He was narrowly defeated in last year’s GOP primary for governor, facing rivals in his own party he charmingly smeared as “establishment pukes,” and playing to racial antagonisms by posing as a champion of Confederate symbols. (Mr. Stewart is originally from Minnesota.) He also pledged to phase out Virginia’s income tax, which accounts for two-thirds of the government’s annual operating revenue, meaning the state would be unable to pay for schools, prisons, parks, police or social services.

He then proceeded to court several notorious white supremacists, blamed “half the violence” last year in Charlottesville on counterprotesters who stood up to neo-Nazis, and said, preposterously, that slavery didn’t cause the Civil War. (No serious historian believes that.)

Respected Virginia Republicans have fled the Stewart campaign, many declining to utter his name. Former senator John W. Warner, once a revered figure in the party, endorsed Mr. Kaine. President Trump, soundly defeated in Virginia by Hillary Clinton, has embraced Mr. Stewart. No surprise there.

Sensing that his campaign is in a death spiral, Mr. Stewart protested that he had been miscast, blamed it all on a campaign aide (whom he fired) and promised that, henceforth, he would project a new, more centrist image — “conservative, strong and stern.” Sadly for him, his narrow base of supporters objected, demanding the old fire, brimstone and toxicity on which Mr. Stewart made (and trashed) his name. By slandering Mr. Kaine, he gave it to them, while giving most Virginians further cause to consign him to political oblivion.