Speaker of the House Nancy Pelosi (D-CA) made a colossal mistake this week by agreeing to an impeachment inquiry before she had seen the transcript of President Donald Trump’s conversation with President Volodymyr Zelensky of Ukraine.

It was a strategic mistake, because the evidence contradicted her claims. But it was also a terrible mistake for the country, because it cast the fairness of the 2020 presidential election into serious doubt.

Trump supporters will rally to support him at the polls — a lesson Democrats should have learned when Republicans lost the 1998 midterm elections in the midst of impeaching President Bill Clinton (who, unlike Trump, had actually committed crimes). Moreover, public support for the inquiry will collapse once the facts are known — through the media fog that is giving the misleading “whistleblower” complaint more credibility than the underlying evidence.

But Democrats hope that impeaching Trump — or even suggesting impeachment — will place a permanent cloud over his head that will make it impossible for him to win in 2020.

If they are right, Trump supporters will look at impeachment as the reason for his defeat. And the fact that Democrats have relied on a CIA source who had no direct evidence of wrongdoing in an attempt to bring down President Trump will be seared into Trump supporters’ collective memory.

The message Democrats are sending is that not only do they refuse to accept the results of the 2016 election as legitimate, but they are willing to use the intelligence community to reverse the results of that election.

In January 2017, before President-elect Trump took office, Senate Minority Leader Chuck Schumer (D-NY) warned: “Let me tell you: You take on the intelligence community — they have six ways from Sunday at getting back at you.” The CIA, and the Democrats, are delivering on that threat.

Of course, Trump had every reason to be suspicious of the intelligence community: they had spied on his campaign and his transition team, and leaked information to the media to undermine him. Outgoing Obama administration officials were hurriedly unmasking U.S. citizens caught on wiretaps, at least one of which was illegally leaked to the media. Then-FBI Director James Comey brought Trump the phony “dossier” — not to warn him, but to intimidate him, and to gather more information from the way the President-elect would react.

Democrats like Rep. Adam Schiff (D-CA) defended the Obama administration’s spying by arguing we had to know if a presidential candidate was “compromised” by a foreign government. (Note the double standard with Biden.)

And the surveillance continued. In the early days of the administration, Trump’s telephone calls with foreign leaders — including close allies, like Australia’s prime minister — were leaked from someone in the intelligence loop. That is the likeliest reason for the White House placing the Ukraine call on a more secure system. The White House knew that the intelligence community had abused its power before and might do so again. (That suspicion was, of course, soon confirmed.)

The Democrats, the media, and rogue CIA agents are making it impossible for Trump to do his job. No foreign leader will talk to our president if he or she knows the conversation will be leaked. That is the real threat to national security, not the contents of Trump’s chitchat with Zelensky.

It is also a threat to our democracy. If Democrats succeed, many Trump supporters will lose faith in the whole system, with dangerous consequences.

That is the Pandora’s box Pelosi has opened. Only a Trump victory can close it.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He earned an A.B. in Social Studies and Environmental Science and Public Policy from Harvard College, and a J.D. from Harvard Law School. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.