Tony Sanchez lobbed an ugly, baseless claim about drug use at his challenger.

In a hateful, last-minute move designed to sow fear in a key Colorado Senate campaign, Republican Tony Sanchez is claiming a vote for his Democratic opponent would lead to heroin injections in the streets of a suburban Denver district.

“Heroin on your street,” reads the campaign mailer that was sent out last week. “Vote against Brittany Pettersen…or she will let addicts shoot up on your streets!”

The Denver Post quickly tagged the Sanchez mailer as one of the five most dishonest attack ads of the entire Colorado campaign season. “Colorado’s political community was incensed” by the mailer, the newspaper reported.

Another Colorado political site, under the headline “Tony Sanchez is disgusting,” wrote that they physically recoiled when they first saw the vicious attack material, which was sponsored directly by Sanchez’s campaign, not by a third-party group.

Colorado’s Gov. John Hickenlooper even weighed in on the local race, after Sanchez’s unhinged material arrived in mailboxes.

“Do not believe the lies and nonsense these negative ads are trying to peddle,” said Hickenlooper. “Brittany Petersen is one of the best people we can have representing [Jefferson Country]. Give her your vote, and vote against attack ads.”

The ugly attack is the all more unseemly because Pettersen, who has served in the Colorado House for six years, has been open about her own mother’s addiction to heroin and opioids.

“Everyone knows someone who’s been affected by this,” Pettersen has stressed, while advocating on behalf of addicts. Pettersen served as the chairwoman of a 10-person bipartisan committee that drafted a package of opioid bills in the previous legislative session.

The desperate mud-slinging comes as Republicans try to maintain their slim, one-seat advantage in the Colorado Senate. The fight between Sanchez and Pettersen is seen as one of five toss-up contests that will decide which party controls the upper chamber next year.

Sanchez, who ran unsuccessfully for the Colorado Senate in 2014, is running something of an odd campaign.

Earlier this year he produced campaign chuckles when he warned that bike baths represent “an attack on you.” Sanchez seemed to be endorsing the right-wing conspiracy theory that bike paths are actually part of a United Nations-backed plan for world domination.

Meanwhile, the candidate remains oddly vague about his resume.

“During an interview this summer, he would not say what he does for a living or whether he has a job,” the Colorado Independent reports.

Sanchez also wouldn’t share his opinion about Trump. “To tell you the truth, I’m just focused on what’s going on locally.”

That, of course, is not believable. But playing dumb about Trump might be a smart move politically, since a recent poll shows him with a dismal 32 percent approval rating among Colorado’s unaffiliated voters, who will likely decide many of the races in November.

They’ll also decide if unhinged GOP attacks about heroin use will get rewarded or penalized.