Last week, after Wednesday’s deadly rampage near Parliament in London, British conservative journalist Louise Mensch tweeted that the terrorist attack has “got everything to do with Russia.” She doubled down Friday on HBO’s Real Time with Bill Maher, propounding the theory, without factual evidence, that allies of the Russian state were stirring up anti-immigrant sentiment in the wake of the attack. “Partisans of Russia were out in the streets saying it was an illegal immigrant who did it, trying to turn the London people against our Muslim friends and neighbor,” Mensch said. One of her fellow guests, MSNBC host Chris Hayes, looked startled by the claim, as well he might since it made little sense. After all, xenophobia in London (as elsewhere) doesn’t require “partisans of Russia.”

Mensch, a former member of Parliament, has made a name for herself as one of the more prominent analysts of the possible collusion between the Trump campaign and the Russian state. She’s found an audience far beyond the conservatives who were her earlier fans, even being granted space in The New York Times for a controversial op-ed on the subject (leading some Times reporters to object to “her baseless claims”). Her increasing prominence is the latest sign that conspiracy theories are no longer exclusive to the far right. “Fraudulent news stories, which used to be largely a right-wing phenomenon, are becoming increasingly popular among those who oppose [Trump],” the Russian-born journalist Masha Gessen, herself a prominent critic of Vladimir Putin’s regime, argued in the Times over the weekend. Gessen cited as an example, “the string of widely shared items that purported to link every death of a more-or-less prominent Russian man to Russian interference in the election.”

This sort of conspiracy-mongering is indeed dangerous, for the same reason that Trump’s outlandish lies are: It corrodes the commitment to truth and honest debate that make democracy possible. And it’s true that, apart from the rise of Mensch and the examples Gessen cited, there are many other reasons to believe the unfolding Russian story is generating an unwholesome willingness to spread unsubstantiated stories. Over the weekend, there was a flurry of Twitter speculation, again without any factual basis, that Trump’s former national security advisor, Michael Flynn, made a deal with the FBI in the ongoing investigation.

Still, Gessen’s critique runs the risk of becoming a facile pox-on-both-your-houses approach that is at odds with the facts. There really is no parallel between Trump’s birtherism (which was based on little more than racism) and concerns about Russian interference in the last election. Leaving aside the wilder theories out there, the core of the Russian story rests on reports from the intelligence community and on well-documented facts about ties between Trump associates and the Russian state. As FBI Director James Comey acknowledged last week, the agency has been investigating possible coordination between the Trump campaign and the Russian state since last July.

Conspiracy theories about Russia are proliferating because of the strange limbo that America finds itself in: The sitting president is under FBI investigation. Further, the president’s party, which is tasked with holding him in check, seems on occasion to be running interference for him. As The Washington Post reports, Devin Nunes, the chairman of the House Intelligence Committee, has withheld key intelligence reports on this matter “from other committee members even while rushing to present it to the White House.” Conspiracy theories about Russia are also proliferating because of the murkiness of the Russian story, the full dimensions of which are hidden because it’s an ongoing investigation and because Republicans are loath to divulge anything that might be politically damaging to their party.

The best way for the media to dispel conspiracy-theorizing about this story would be to take great care with facts and characterizations. Gessen, for instance, mars her otherwise solid critique by going after Congressman Adam Schiff. “This past Monday, Adam Schiff, the ranking Democrat on the House Intelligence Committee, opened a hearing on Russian interference in the election with a speech that seamlessly mixed verified information with rumor and exaggeration,” Gessen wrote. But she cites no evidence of rumor and exaggeration. In truth, Schiff has been extremely careful and responsible in his comments, and has played an exemplary role in trying to ensure that his committee acts in a responsible, bipartisan way.

This spate of conspiracy theories has a political origin: Trump’s extraordinary secrecy about his finances and business connections. Since this problem was created by politics, it ultimately will have a political solution: The FBI will make a judgment, and, if anyone in the Trump administration is implicated, Congress will have to decide if punishment is merited. The best way for political leaders to counter these conspiracy theories is to do their job, which means preventing any attempts at a coverup (which, after all, is what brought down President Richard Nixon). That responsibility may fall to Democrats, who could take a proactive role by pushing Nunes to be removed as chairman of the House Intelligence Committee. And if there is an attempted cover-up, Democrats and law enforcement officials could easily leak the truth to the media.

Rather than decrying conspiracy theories as a blight caused by both sides, it’s crucial to solve the political crisis that is causing them to proliferate.