Washington — In the spirit of the political season, I want to claim credit for the most STUPENDOUS, INSIGHTFUL and POWERFUL political strategy since Pericles bound the DELIAN LEAGUE into an empire to resist THE PERSIANS. I urged voters to support reasonable Republican candidates in the Senate, and to vote for every Democrat in House races. And the country rose up in TOTAL VINDICATION of my IDEOLOGICALLY INCOHERENT but PERFECTLY PRACTICAL suggestion for strategic voting.

Judged purely by its outcome, the 2018 midterm election was significantly north of acceptable. Any evening in which future former congressman David Brat and appears-to-be-ousted Dana Rohrabacher — who help constitute the right wing of GOP lunacy — feel dejected is emotionally satisfying. The Democrat-controlled House of Representatives will be a check on an administration in desperate need of checking. At the same time, the Senate will continue its originalist shift in the federal courts — the support of which separates conservative Never Trumpers from those who have simply become liberals.

With an economic growth rate above 3 percent, and an unemployment rate below 4 percent, and a relatively peaceful world — and following a Supreme Court nomination battle that rallied and united the GOP — the president and his party lost control of the House. The #MeToo movement rolled along, bringing the voices of younger women to Washington. Democrats carried independent voters. The “blue wall” was partially reconstructed in Michigan, Pennsylvania and Wisconsin. It was, by any standard, a major defeat for the Republican Party. Or, as Donald Trump calls it, a major victory.

But this acceptable midterm outcome disguised disturbing trends — like a patient who is entirely healthy except for a touch of leukemia. Trump’s final political appeal — literally warning that brown people were invading the country and promising they would be shot — was both Trumpism and racism unadulterated. His base of support — millions of people, skewing white and male — found this message compelling. When he called his former alleged mistress a “horseface,” or separated migrant children from their parents, or rounded up migrant children in a desert prison camp, his supporters responded “Hell yeah!” in sports bars and (God help us) evangelical churches across Trump country. They did this because Trump talks like them, and tells it like it is, and defies political correctness, and doesn’t take any crap from anyone — some of the most insipid justifications in the history of American populism. These explanations make Free Silver look like a compelling cause in comparison.

No serious political prognosticator — and there are a few — thinks that this appeal to this group of shrinking voters can possibly win national elections 10 or 20 years from now. By making the GOP the party of misogyny, anger and bigotry, Trump is systematically alienating large and growing portions of the electorate. He is dividing old from young, and white from minority, and men from women, and rural from urban. And when Republicans are left with a political coalition concentrated among aging, paunchy, male Caucasians (my demographic group), Trump will be long gone from politics. Like many narcissists, he will leave a trail of ruin behind him, and care not one whit.

Trump has not found a new and creative way to win. He is rallying a coalition that was at its most potent in 1988 for one, last, bitter, alienating hurrah. He may undermine the viability of the Republican Party in the process. More than that, he has ripped open old wounds of race and gender that threaten the unity and justice of our country.

Democrats have now been given a stage, a platform, to demonstrate a better way. But they have a fateful choice. On one hand, they could elect an off-putting, polarizing House speaker from the past, prove unable to distinguish between useful oversight and partisan harassment, and be riven by internal debate over impeachment after special counsel Robert Mueller’s report. Or … OK, let’s face it; Democrats will do all these self-destructive things. It is the shared addiction of recent American politics to interpret partisan wins as opportunities to achieve absolute ideological victory, rather than build a broader coalition.

The most important test will come in the 2020 presidential nomination process, which has already begun. Here is the hard, political reality for Democrats, unchanged by their recent House victory: Faced with a choice between a scary, quasi-socialist culture warrior of the left and a scary, right-wing, nativist buffoon, America’s current presidential electorate may well choose the latter. And this would grant a racist demagogue the BIGGEST VICTORY OF HIS LIFE.

— Michael Gerson is a columnist for Washington Post Writers Group.