The Democrats believe that the 2020 election is too important to be left to the voters. It’s obvious that President Trump withheld defense aid to Ukraine to pressure its president to commit to the investigations that he wanted, an improper use of his power that should rightly be the focus of congressional investigation and hearings.

Where the Democrats have gotten tangled up is trying to find a justification that supports the enormous weight of impeaching and removing a president for the first time in our history.

They’ve cycled through different arguments. First, Trump’s offense was said to be a quid pro quo — a phrase cast aside for supposedly being too Latin for the public to ­understand. Then it was bribery, which has lost ground lately, presumably because of the inherent implausibility of the charge.

Now, the emphasis is on Trump’s invitation to the Ukrainians to “meddle” and “interfere” in our elections.

This is posited to be an ongoing threat. Nancy Pelosi said in her statement calling on the House to draft articles of impeachment: “Our democracy is what is at stake. The president leaves us no choice but to act, because he is trying to corrupt, once again, the election for his own benefit. The president has engaged in abuse of power undermining our national security and jeopardizing the integrity of our elections.”

House Judiciary Committee Chairman Jerry Nadler said on “Meet the Press” last weekend that Trump has to be impeached “for posing the considerable risk that he poses to the next election.” Asked if he thinks the 2020 election will be on the up-and-up, he said, “I don’t know. The president, based on his past performance, will do everything he can to make it not a fair election.”

The gravamen of this case is that the election is too crucial to allow the incumbent president of the United States, who is leading in key battleground states and has some significant chance of winning, to run. In fact, the integrity of the election is so at risk that the US Senate should keep the public from rendering a judgment on Trump’s first term or deciding between him and, say, his nemesis Joe Biden.

Of course, it’s possible to imagine a circumstance where a president would indeed present such a grave risk to our elections that he’d have to be removed. This is a reason that we have the impeachment process in the first place.

But what’s the real harm that Trump’s foolhardy Ukraine adventure presented?

Let’s say that Ukraine had, in response to Trump pressure, actually announced an investigation into Burisma, a shady company that had in the past been under investigation. What would have happened? Would Joe Biden have been forced from the race? Would his numbers have collapsed in Nevada and South Carolina, his best early states? Would his numbers have changed anywhere?

No, it’s not even clear there would have been any additional domestic political scrutiny of Hunter Biden’s lucrative arrangement with Burisma, an issue that is dogging the former vice president on the campaign trail anyway — because his son’s payday was so clearly inappropriate.

The bottom line is that after tsk-tsking Trump for refusing to say in advance that he’d accept the outcome of the 2016 election, Democrats have steadfastly refused to truly accept the 2016 result, allegedly the work of the Russians, and now are signaling they won’t accept next year’s election, either, should they lose again.

Given their druthers, Trump wouldn’t be an option for the voters. They are rushing their impeachment, in part, because they know that as November 2020 approaches, it becomes steadily less tenable to portray the man who wants to run in an election as the threat to democracy and the people who want to stop him as its champions.

With every day that passes, the Democrats risk a growing perception that they themselves are a threat to the 2020 election.

Twitter: @RichLowry