With both parties trying to put their best foot forward for November's general election, here are five things to watch in this summer's preliminary elections. (Video: Jenny Starrs/The Washington Post, Photo: Chuck Burton/The Washington Post)

The Republican Party’s dance with President Trump has long been marked by fits and starts. And for much of that troubled relationship, it has been hard to grasp why so many conservatives would sell their political souls to a man who wallows in racist stereotypes, questions federal judges’ legitimacy, flogs the free press, undermines Madison’s constitutional norms, declares war on America’s intelligence community, and attacks Justice Department and FBI leaders he appointed for refusing to kill special counsel Robert S. Mueller III’s investigation.

With the GOP’s midterm campaign pitch coming more clearly into focus, we may be starting to get our answer.

Proving just how cynical swampland politics can be, most of the Republican politicians and lobbyists debasing themselves daily for Trump once treated the reality-TV star with open contempt. House Speaker Paul D. Ryan (R-Wis.) declared a Trump comment to be a “textbook” example of racism before quickly endorsing him. Mike Pence told friends and political allies that the New York billionaire was an unacceptable Republican nominee before eagerly accepting a spot on Trump’s ticket. And craven conservatives who once blasted “Morning Joe” for giving presidential candidate Trump airtime now attack us for criticizing President Trump’s White House antics.

Few things in politics are black and white, but for members of Lincoln’s party, opposing Trump should have been one of them. On Dec. 7, 2015, the former Democratic donor called for a “total and complete shutdown of Muslims entering the United States . . . . ” For me, that was it. Who could, after all, vote for a politician who wanted to ban 1.5 billion souls from the United States because of their religious faith? Not me. The fact that Republicans such as Senate Majority Leader Mitch McConnell (R-Ky.) and Ryan still support Trump reveals more about their character than mine.

Even after his calling for a Muslim ban in 2015, professing ignorance of former Ku Klux Klan leader David Duke in 2016, defending white supremacists in 2017 and calling out Hispanic “breeding” in April, Trump still enjoys steadfast support among most Capitol Hill Republicans. Many GOP politicians are so affected by his corrupting influence that they forced the Justice Department and the FBI to expose a source while desperately trying to derail the government’s investigation into Russian attacks on America’s democracy.

Good luck explaining that to your grandkids, Speaker Ryan.

For much of Trump’s reign over Republicans, party members got little more from their dance with The Donald than a Supreme Court appointment. But as Trump careens toward his first midterm test in November, Democrats should understand that they are in for a fight. The blundering billionaire has actually begun to fill his political trophy case with victories sure to inspire the conservative base.

Republican candidates justifying their support for a man who lies about payoffs to porn stars, lies about policies that rip infants from their mothers’ arms and lies about the existence of White House staffers speaking on his own behalf now have more than Supreme Court Justice Neil M. Gorsuch to justify their devotion to the “carnage” president.

For starters, they can point to Trump’s conservative judicial nominees beyond Gorsuch as cause for celebration. But their talking points can also include massive tax cuts, a bigger military budget, regulatory reform and the gutting of the Environmental Protection Agency. Other wedge-issue winners include the planned withdrawal from the Paris climate accords, scrapping of the Iran nuclear deal, undermining Obamacare, moving the U.S. Embassy in Israel to Jerusalem, attacking federal employee unions and promoting extreme immigration policies. Add to that the mocking of political correctness and identity politics, and you have a platform sure to inspire the activists who drive today’s Republican Party.

While many of these policies will drive up the federal debt and diminish U.S. power across the globe, and will likely be reversed by a stroke of his successor’s pen, Trump’s list of “accomplishments” are scratching an ideological itch that establishment Republicans could never reach. This is, of course, because many of his moves will prove to be disastrous in short order. But Trump is not concerned with history’s judgment. He simply wants to stay out of jail and complete his first term.

Keeping control of Congress after the midterms may allow the president to achieve those modest goals. But the question Democrats should be asking themselves today is whether Trump’s expanding populist checklist will energize the conservative base in November enough to keep his congressional handmaidens in charge. Unless Democrats find their voice and an alternative to Trump’s bleak agenda, his pathetic populist shtick just may do the trick this fall.

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Read more:

Michael Gerson: The cowardice among Republicans is staggering

The Post’s View: GOP leaders’ complicity grows as members undermine the rule of law

Dana Milbank: Republicans finally reveal their red line for Trump

Dan Schwerin: Three steps Republicans should take to start reining in Trump