The ominous aspect of that Trump campaign rally cry of “Send her back!” in North Carolina seemed to come from the crowd itself, with Donald Trump benignly listening in silence as it swept over him.

All he had to do was mention of Democratic Rep. Ilhan Omar of Minnesota, one of the four congresswomen he previously invited to “go back” to where they came from. Saying her name, without overtly urging the crowd, unleashed that ugly demand and provided the kindling for the bonfire of hate that presages his 2020 re-election strategy.

For 13 seconds thereafter, Trump stood tight-lipped as the functional equivalent of his 2016 “Lock her up!” takedown of Hillary Clinton rolled over the rally audience. He didn’t need to lead the chorus, already conditioned by Trump’s now well-established mantra for inciting mass vitriol and vindictiveness.

He subsequently followed with yet another bald-faced lie that he tried to quiet the venomous outcry, and that he “wasn’t happy” about it. The crowd’s chant was precisely the response predictable from his attack on these four American citizens, three of whom were born in this country. Omar was naturalized as a teenager.

The only mystery is why the president sought to create the impression that he was surprised that his racist assault on the four might be seen as the match that ignited the fire of hate among the assemblage.

It was a visible and audible confirmation that after nearly three years of his presidency, his mad-as-hell constituency of anti-immigrant and racially hostile voters is ready to use its strength at the ballot box next year to give him four more years in the Oval Office.

The critical question is whether his political base remains strong enough, and whether it can be expanded enough in 2020, to pull off another victory for him.

With polls continuing to indicate Trump plateauing at a bit more than 40 percent of the popular vote, once again his chances may well lie in the Electoral College, where success in a few targeted interior states enabled him to overcome the popular vote loss of about 3 million votes to Clinton in 2016.

The evidence at last week’s Trump rally that his supporters are ready and willing to follow the same game plan based on hatred and vitriol is an ominous hint of what may happen again in the continuing national climate of an angry and divided electorate.

Much may well depend on whether the Democrats can maintain the momentum of the 2018 midterms and recapture the Senate next year. Such an outcome is at the heart of House Speaker Nancy Pelosi’s game plan of slowing the rush of some Democrats to impeach Trump.

Trump’s clear signal from last week’s rally is a warning to Democrats that they must fashion their effort to oust him with more than mere knee-jerk mutual hate over his ugly and intemperate racist remarks.

The Justice Department’s defiance toward Congress’s congressional mandate to enforce subpoenas for high administration officials’ testimony on Trump’s broad range of illegalities is itself grounds for impeachment. It impedes the lawful conduct of the people’s business — the president’s principal obligation.

How much longer can this bootleg outrage be allowed to go on?

——

Jules Witcover’s latest book is

“The American Vice Presidency: From Irrelevance to Power,” published by Smithsonian Books.