There are indelible details, admittedly sometimes exaggerated, that shape our memories of every presidency:

A drunk Richard Nixon talking with the White House portraits. Jimmy Carter monitoring who used the White House tennis courts. George H.W. Bush looking baffled by a supermarket scanner. Bill Clinton … nah, let’s not go there. Barack Obama limiting himself to just seven lightly salted almonds a night.

For Donald Trump, it may be the image of the 45th president tromping around the empty family quarters of the White House at night, clad in a bathrobe, brooding about his enemies and plotting revenge on Twitter. This portrait of Trump (captured by New York Times reporters Glenn Thrush and Maggie Haberman) suggests a president haunted by the loneliness of his electoral victory.

The last few days have been the time when it should have dawned on everyone — even the craven and the credulous — that there never will be a normal interlude with Trump in the White House.

He took what should have been a bland pre-Super Bowl interview with Bill O’Reilly and managed to imply that American presidents have as bloody hands as Vladimir Putin. And in a series of explosive tweets, the president excoriated the “so-called judge” who halted enforcement of his draconian immigration order and warned that “if something happens, blame him and the court system.”

Then on Monday, speaking at an Air Force Base in Florida, Trump accused the media of deliberately covering up terrorist attacks: “The very, very dishonest press doesn’t want to report it. They have their reasons.”

Hitting below the belt

Even by the low-bar standards of Trump, these were low blows. It is dangerous to loosely throw around the epithet “un-American.” But it is hard to find another adjective to describe Trump’s embrace of the thuggish Russian autocrat and his contempt for the legitimacy of a federal judge appointed by George W. Bush, who was unanimously confirmed by the Senate. Trump’s latest attack on the media defies logic — unless the conspiracy theorist in chief somehow believes The New York Times and CNN are controlled by jihadists.

Remember this is Trump during what should be his honeymoon period.

The only new foreign policy problems facing America are of Trump’s own making like the president’s intemperate phone conversation with Australian Prime Minister Malcolm Turnbull. The Senate has yet to reject any of his appointees with Betsy DeVos poised to be confirmed Tuesday with the help of Mike Pence’s tie-breaking vote. And congressional Republicans, throwing ideological consistency to the winds, have suddenly become permissive about a president trying to govern through executive orders rather than legislation.

So far, Trump has limited himself to bilious words and tweets. But a president this restless and peripatetic — egged on by in-house anarchists like Steve Bannon — is unlikely to stop there. And the biggest question hanging over our democracy is: What then?

So-called Supreme Court

What if the eight-member Supreme Court rules against Trump’s immigration orders and the president vows his defiance? What if Putin moves farther into Ukraine or actively destabilizes the Baltic states — and President Trump cheers him on? What if the Trump Justice Department begins mass prosecutions of journalists for publishing leaks?

Frighteningly, these scenarios are not lifted from dystopian fiction. They are merely the logical extension of what Trump has been saying from his bully pulpit in the White House.

These represent different kinds of threats than Trump eviscerating the Dodd-Frank financial legislation, approving the Keystone XL Pipeline, or rolling back Obamacare. Such policy reversals are what happens when a party loses a presidential election and fails to make enough gains to win back the Senate.

But the looming danger is when Trump goes far beyond where any other would-be Republican president (Jeb Bush, Marco Rubio or even Ted Cruz) would have thought to tread.

That is why I am a passionate believer in Big Tent Anti-Trumpism.

The goal has to be to assemble the broadest possible coalition of Democrats and fair-minded Republicans to oppose any direct Trump attack on the tenets of American democracy. If the independence of the judiciary, the survival of a free press or American commitment to NATO is on the line, you shouldn’t care whether your allies share your views on abortion or the ideal marginal tax rate.

But many liberal activists, reflecting their understandable frustrations, are demanding litmus-test purity from Democrats in Congress. Already, Tea Party-like demonstrations of the left have been held at the Brooklyn home of Senate Minority Leader Chuck Schumer and the office of Missouri Sen. Claire McCaskill, who faces a tough re-election fight next year in a state that no Democratic presidential candidate has carried in this century.

In normal political times, it might make sense for left-wingers to pressure senators like Schumer and McCaskill not to go wobbly. But these are not normal times, which ideally should constrain the “if it feels good, do it” style of political protest.

The emphasis for Democrats has to be on two unrelated, but linked, goals involving the word “democratic” in both its lower-case and upper-case forms. That is, reaching out to everyone, regardless of political philosophy, who is appalled at Trump’s assault on democratic norms — and winning as many Democratic congressional seats as possible in 2018.

There are those who argue that almost all Republicans have made their Faustian bargain with Trump and cannot be trusted to resist anything this side of a military coup. But if partisanship invariably trumps principle, we are already doomed as a democracy.

I prefer to believe — and the spontaneous immigration protests at airport reaffirmed my faith — that most Americans support democracy and diversity. Which is why I am proudly casting my lot with Big Tent Anti-Trumpism.

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and the Washington Post. His book on his con-man great-uncle was just published: “Hustling Hitler: The Jewish Vaudevillian Who Fooled the Fuhrer.” Follow him on Twitter @MrWalterShapiro.