Richard L. Hasen is Chancellor's Professor of Law and Political Science at UC Irvine School of Law and author of " Election Meltdown: Dirty Tricks, Distrust, and the Threat to American Democracy ." The opinions expressed in this commentary are his. View more opinion on CNN.

(CNN) The United States Senate is poised to acquit President Donald Trump on what will likely be a near party-line vote after a witness-free impeachment trial in which he will be cleared of charges that his solicitation of foreign interference in the 2020 presidential election and obstruction of the House's investigation justified his removal from office.

But while the impeachment and trial will soon be behind us, the behavior of Senate and House Republicans have increased the chances of an election meltdown in November.

Think about what happened this week with Democrats' inability to run a successful Iowa caucus system, and conservative activists' conspiracy theories that immediately arose suggesting, without evidence, an attempt to rig the vote.

The impeachment ordeal has three key implications for the integrity of the 2020 elections, each one more troubling than the last.

Lesson 1: The President cannot be counted on to deter foreign interference and may even encourage it again. One would expect a normal president to be circumspect and chastened after an impeachment by the House and trial in the Senate, and to avoid those activities, going forward, that put him under investigation in the first place.

But we know this is no ordinary president. After all, Trump publicly called for the Russians to break into Hillary Clinton's email server during the 2016 elections and leak its contents, one of a series of actions leading the Robert Mueller investigation to look into potential ties between the Trump campaign and the Russians.

And while special counsel Mueller found that there was no coordination between the two, he still found that Trump's "campaign expected that it would benefit electorally from information stolen and released through Russian efforts."

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Trump was undeterred by Mueller's investigation, telling ABC News's George Stephanopoulos that "I think I'd take it" if offered dirt on an opponent in 2020. It is no surprise then that the President pressured Ukrainian leaders to announce a potentially phony investigation into Joe Biden, one of Trump's key political rivals. Nor is it a surprise that even during the controversy surrounding these efforts with Ukraine, Trump, on camera, encouraged the Chinese government to investigate Biden too.

Now, with the Senate trial behind him, the President can go right back to soliciting foreign interference in the 2020 elections. He would likely be thrilled if the reporting is true that t he Russians have infiltrated servers at Burisma, the Ukrainian energy company at the heart of the Biden faux-scandal in Ukraine.

We know from recent French elections that the latest Russian tactic is to sprinkle falsified documents within whatever they might leak to Western sources. Indeed, the Russians or others could do even worse. In one possible scenario I've spun out , based upon Russian activities in Ukraine beginning in 2015, Russians could seek to interfere with the American power grid in a Democratic city in a swing state on Election Day in 2020.

Lesson 2: Republicans in the Senate can be expected to back up Trump lies about 2020 election results. It is quite possible that Trump will be ahead on election night in a swing state like Pennsylvania only to see his lead evaporate over the days after election day, as new absentee ballots are counted. That's not because there is fraud but because it takes a while to process and count absentee ballots, and in recent elections It is quite possible that Trump will be ahead on election night in a swing state like Pennsylvania only to see his lead evaporate over the days after election day, as new absentee ballots are counted. That's not because there is fraud but because it takes a while to process and count absentee ballots, and in recent elections such ballots have tended to be Democratic.

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If Trump were to lie and say he has won the election when it is clear that he lost, Republicans could go along with the lie despite objective evidence to the contrary. We saw this time and again with many Republican members of Congress and senators denying the undisputed facts that the President conditioned a meeting with Ukraine's President upon Ukraine announcing an investigation into Trump's political rival, Joe Biden.

During the Senate hearing, in one breath Republican senators claimed Democrats failed to produce new evidence showing the President engaged in a quid pro quo and in the other, they denied Democrats the ability to introduce new evidence that they had.

Given the Senate and House Republicans' willingness to back up Trump lies, consider the following scenario for election night in November 2020: Trump claims he won Pennsylvania because he is ahead in the vote count on election night (Pennsylvania is a state again decisive in the presidential election).

As the vote counting continues, he loses his lead to the Democratic rival. Trump could claim that the subsequent count was the result of voter fraud, despite a lack of evidence to back up the charge, and then seek to get the Republican-dominated Pennsylvania legislature to send a competing slate of presidential electors choosing him to the electoral college.

Under byzantine rules for counting electoral college votes -- rules that favor the Republicans -- Congress could choose Trump despite the votes of the people of Pennsylvania. The Republicans' performance during impeachment in both the House and Senate shows they could be shameless.

Lesson 3: The country is seriously polarized and facts themselves are up for grabs. The partisan reactions to impeachment show that the country is divided into two universes: one in which the President can do no wrong and one in which he is perhaps the worst President to ever serve in the office.

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To Democrats, the impeachment trial was about stopping Trump from cheating in the 2020 elections. To Republicans, the trial was about Democratic efforts seeking to relitigate the 2016 elections results that they have never fully accepted.

Nearly half the country is going to be profoundly disappointed with the results of the 2020 elections, however it comes out. There are no longer good intermediaries accepted by all sides who can appeal for calm and persuade losers to accept fair election results in the event of a very close election.

Politics has become warfare by other means, and the impeachment trial looks to be a warmup for an epic battle over the 2020 elections, which might not end on election day. As with impeachment, we cannot count on cooler heads to prevail.