At our political costume ball, it is definitely '90s nostalgia night. A president obsessed with attacking all things Clinton stands accused of serial sexual harassment, sends out underlings to dismiss the accusers as liars, condemns a federal investigation as a politically motivated fraud and is attempting to destroy the reputation of the leader of that investigation. Hillary Clinton may be Donald Trump's continuing target, but the Clinton years are clearly his inspiration.

It worked the first time around. In Bill Clinton's case, the Democratic Party almost uniformly honored tribal loyalties above legal or moral principle. Even the feminist left generally fell into line for partisan reasons. "American women," said columnist Nina Burleigh, "should be lining up with their presidential kneepads on to show their gratitude for keeping the theocracy off our backs." What is a little sexual misconduct and obstruction of justice among friends when legal abortion is at stake?

Now Trump appeals to the same type of team solidarity, this time on the right. "The Dems are using this terrible (and bad for our country) Witch Hunt for evil politics," tweeted Trump, "but the R's are now fighting back like never before." Note how a federal investigation of Russian influence on American democracy has become "the Dems." Note also that it is not the president and his lawyers fighting this investigation but the "R's." Trump is conditioning Republicans and conservatives to view his upcoming legal defense entirely through the lens of partisanship. With the broad cooperation of conservative media, there is every reason to think he might succeed.

Trump's ultimate objective in all this matters greatly. If he wants to recruit Republicans into a defense of the shady political and business dealings of Paul Manafort and the rest of the president's political circle — now exposed by federal indictment — it will be discrediting and humiliating. A party that rallies to the defense of corruption will eventually be seen as a swamp in need of clearing.

But if Trump's goal is to escape a tightening legal investigation by firing special counsel Robert Mueller and issuing a string of self-protective pardons, the participation of the Republican Party takes on a different meaning. In this case, Trump would be turning his authoritarian pose into authoritarian practice, removing an essential check on the abuse of power. Liberal democracy itself would be under attack from an American Putinism. And elected Republicans who enabled this would be complicit in a crime against the Constitution and violate the oath they took to defend it.

As the indictments begin to come down, Republicans need to ponder what legal and ethical lines, if any, they are willing to draw. Continuing the attacks on Hillary Clinton's own dishonest dealings is all fun and games (except to Clinton, I suppose). Joining the defense of slimy political figures such as Manafort makes one, ceteris paribus, into a slimy political figure. Obscuring or excusing Russian influence on the American political process is a dangerous disservice to the country. Supporting Trump in a power play against the special counsel and his investigation would be an attack on the stability and legitimacy of the Republic — a source of infamy in American history.

To what circle of hell are Republican officials about to consign themselves? It would be useful for members of Congress to declare that they will never enter the fourth circle — the demolition of the integrity and independence of the FBI — if only to deter Trump from forcing a constitutional crisis.

Do Republicans and conservatives really want to be remembered as a bodyguard of enablers for this man? For this cause? Few enter the fray of political ideas, or make the considerable sacrifices of entering public life, to defend corruption and the abuse of power. That is now the calling of the Republican partisan, and the downward path of dishonor.

— Michael Gerson is a nationally syndicated columnist. His email address is michaelgerson@washpost.com.