Among the many allegations of President Trump's ties to Russia, some of which the FBI is currently investigating, this ranks among the least legitimate.

When an unverified dossier put together by a former British spy suggesting that the Russians had personal dirt on President Trump became public late last year, most major news organizations (including The Washington Post) did not even publish the claims because they were, well, unverified.

And yet Rep. Maxine Waters (D-Calif.), the top Democrat on the House Financial Services Committee, is sure that some of the more salacious allegations in it are true.

"We already know that the part about the coverage that they have on him with sex actions is supposed to be true. They have said that that's absolutely true," she told MSNBC's Ali Velshi in an interview Thursday, as brought to our attention by the New York Times' Sopan Deb.

It's not clear who "they" or "them" are. When Velshi asked Waters for evidence, her reply was: "Yeah, but you understand that I am saying the investigations must be done," adding: "I do think that impeachment will be necessary." As for the "sex actions" Waters says she "knows" are true, well, we can't even go into those here because we have no evidence that any of it actually happened.

An aide to Waters told The Fix that she was referring to an episode the dossier says was confirmed by a source whose information is redacted in the dossier. The aide said Waters was emphasizing her support for  investigation into the redacted source and the information that source provided.

"She wasn't talking about anything that's not already in the public domain," the aide said.

What strikes us odd about Waters's claim is how closely it adheres to a formula followed by the president she so often criticizes: Make an eyebrow-raising claim. Provide zero evidence. Ignore the fact you have no evidence. Demand an investigation to vindicate you.

Trump has done that several times since becoming president, most recently on allegations of massive voter fraud and claims that then-President Barack Obama wiretapped his phones at Trump Tower during the 2016 campaign.

For both Trump and Waters, the likelihood of investigations into their as yet evidence-free claims is slim. What's more likely is that what they threw out as fact will remain in the murky world of conspiracy theories, for either side to pick up and run with when it suits them politically.

"We are all conspiracy theorists now," writes The Fix's Chris Cillizza.

What we know about the dossier, especially its most salacious claims, seems to fall into that category. The Post's national security team wrote in January: "The dossier was provided to multiple news outlets, including The Washington Post, which pursued numerous leads, including overseas, but could not substantiate its allegations." Only BuzzFeed published it, to much criticism.

What Waters claims to be true is so without actual, you know, evidence that intelligence officers' decision to even brief Trump and Obama on the dossier's existence was controversial. Some national security officials argued that it would be a dereliction of duty not to tell the incoming president that this was out there, while others made the case that the dossier blurred the line between fact and innuendo.

Whatever the reality, it was explosive. After the fact that he was briefed on the dossier was leaked to the press, Trump lashed out at the U.S. intelligence agencies he now leads:

While the U.S. intelligence community has concluded that Russia meddled in the presidential election to try to help Trump win, it has not determined that the dossier's claims are true.

All of which is why what Waters said arguably undermines Democrats' unofficial Michelle Obama-derived motto for how to respond to a time when most political norms have been thrown out the window: “When they go low, we go high.”

I made the same argument when Rep. Cedric Richmond (D-La.) said top Trump adviser Kellyanne Conway "really looked kind of familiar" kneeling on an Oval Office couch. (He later apologized.) And I implied as much when Sen. Bernie Sanders (I-Vt.) flat-out said the president was "shamelessly lying" the other day. (Sanders strongly disagreed with me.)

It's not that politicians can't say what they think. But my point is our political discourse would be much better served if they offered up concrete evidence of their claims. Right now, both sides seem to be eschewing that norm in favor of politically expedient hits on each other based on limited — or no — actual facts.

Rep. Maxine Waters (D-Calif.), who skipped the inaugural ceremonies, lambasted President Donald Trump's Cabinet nominees at the Women's March on Washington (The Washington Post)