Talk to a supporter of President Donald Trump and, at some point in the conversation, you are likely to hear some version of this riff: “The mainstream media is fake news. They ignore all the good things Trump is doing because they hate him and wanted Hillary Clinton to win. That’s why they spend so much time on this Russia story and not enough time investigating whether Trump Tower was wiretapped!”

Talk to an opponent of Trump and, at some point in the conversation, you are likely to hear some version of this riff: “Russia has something on Trump. Michael Flynn, Jeff Sessions, Paul Manafort and the president’s own unwillingness to bad-mouth Vladimir Putin and Russia all make clear that he is being secretly controlled by a foreign power. He needs to be impeached!”

We live in an “X-Files” time. Conspiracy theories aren’t dismissed; instead, they are taken as something close to fact.

Conspiracy theories have always been with us — there was a second shooter in the JFK assassination, 9/11 was an inside job — but have almost always existed on the fringes of political dialogue. Not anymore. We are all conspiracy theorists.

Here’s what Paul Musgrave, an assistant professor at the University of Massachusetts Amherst, wrote in a piece for The Washington Post website:

“Less than two months into the administration, the danger is no longer that Trump will make conspiracy thinking mainstream. That has already come to pass. Conspiracy theories, rumor and outright lies now drive the news cycle . . . Far worse, such untruths may now be driving government policy in realms as disparate as immigration policy and civil rights.”

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Trump’s roots in politics are closely tied to his willingness to embrace conspiracy theories. His candidacy was made possible by his embrace of the disproved idea that former President Barack Obama wasn’t born in the United States. During the 2016 campaign, he regularly brought conspiracy theories to the center of the conversation. He suggested that Sen. Ted Cruz’s father was part of the plot to kill John Kennedy.

That conspiracy flirtation has continued in his presidency, with the wiretapping tweets as the prominent example. Trump seems comfortable taking a conspiracy theory and, with scant evidence that it is anything more, pushing it into the mainstream. And, now the Trump White House is trying to claim victory and move on, insisting that his only goal was to get congressional committees to look into the allegations in search of evidence he insisted he already had.

What Trump knows is that for many of the people who support him, the fact that he has not offered any evidence of the wiretapping is besides the point. Of course the evidence isn’t readily available — the political establishment is doing everything it can to cover it up and make Trump look bad!

On the other side of the political spectrum, there is the growing sense among Democrats that Trump is in hock to the Russian government. That Trump’s former national security adviser and attorney general both misremembered conversations they had with Russian Ambassador Sergey Kislyak is taken as certain evidence of this fact. As is the fact that Trump refuses to call for an independent investigation into the ties between Trump’s campaign and Russia.

As always, conspiracy theories could be true! The most prominent example is the reporting the National Enquirer did in the 2008 presidential campaign about a child then- Sen. John Edwards fathered out of wedlock.

But, for every one conspiracy theory that winds up being right, there are a thousand — or a million — without merit. That used to be a sentence that 98 percent of the population could agree on. No longer.

Conspiracies grow and grow. And we believe them in ways we’ve never done before.

Chris Cillizza writes “The Fix” political blog for The Washington Post.