It has become easy to understand Donald Trump’s affection for coal miners. The president and the miners work underground — and each week Trump finds a way to descend to new depths.

As Trump heads to Florida on Wednesday for a “listening session” with students, it is important to remember the president’s most egregious recent mouth-off session.

That was his inflammatory Saturday tweet in which he suggested that the FBI could have prevented the Parkland massacre if the Bureau were not “spending too much time trying to prove Russian collusion with the Trump campaign.”

The Republican attacks on Trump for implying that the FBI has blood on its hands were delivered in the muted tones of a parent not wanting to wake a sleeping baby.

Typical was South Carolina Sen. Tim Scott, who took pains to say on “Face the Nation” that the Florida shooting and the Russia probe were (drum roll, maestro) “two separate issues.” Only outgoing Ohio Gov. John Kasich — who represents a branch of the Republican Party that may no longer exist — had the gumption to tell CNN that Trump’s tweets were “absurd.”

No excuses

It is easy to conjure up the excuses that congressional Republicans murmur to themselves as they stay silent in the face of Trump’s outrages.

“I am in Congress — and not working in the White House. I’m not responsible for everything that Trump says.”

“Trump’s just bored and blowing off steam. The best thing to do is to ignore it.”

“With the Democrats piling on, I’m not going to criticize a Republican president.”

“What’s the upside to getting involved for me?”

“I’m in a tough re-election fight. The last thing I need is to split the GOP base.”

“What if Trump starts attacking me on Twitter?”

“Now just isn’t the time. I’ll save my ammunition for later.”

This collective timidity has contributed to a presidency that refuses to take any steps to protect the sanctity of American elections in 2018 and beyond.

The Trump White House has been handing out temporary security clearances like they were valet parking receipts at Mar-a-Lago. Yet the silence from congressional Republicans over special treatment for Jared Kushner (the presidential son-in-law with the error-filled financial disclosures) has been deafening.

Even without mentioning the name Robert Mueller or the dread noun “collusion,” responsible Republicans (alas, a dwindling breed) must be troubled by the blithering incompetence of the chaos-theory Trump White House. How many unfilled jobs in the administration and incoherent public statements on legislation does it take to undermine confidence in a president?

Granted, for Republicans who believe in income-transfer programs (as long as the money heads to the already wealthy), the tax bill represented an excuse to maintain a semblance of party discipline. But now the 2018 legislative agenda is pretty much reduced to naming federal buildings.

Daisies will be bursting through the sidewalks on the Capitol grounds and unicorns will be grazing on the Mall before Congress approves Trump’s hollowed-out plan for America’s hollowed-out infrastructure. And all Trump did was sow discord as the Senate tried to codify legal protections for the Dreamers, undocumented immigrants who came here as children.

Maybe as periodic rumors bubble to the surface about the possible retirement of Anthony Kennedy — the swing justice on the Supreme Court — Senate Republicans might still feel the need to band together for a potential confirmation fight.

But the line, “I’m supporting Trump because of the courts,” doesn’t carry much weight in the House, where members have no constitutional role in approving federal judges.

Through the looking glass

It is possible that I am missing the reality that Republicans in Congress are being sincere — that, in the blink of an eye, they have collectively all become nativist opponents of immigration, fierce foes of free trade and isolationists thrilled at the notion that Russia and China will be running the world.

Could they all be mesmerized by the globe-girdling vision of a former reality show host who is bumping along with a presidential approval rating just above 40 percent? Has the Republican Party become the Trump Party simply because the congressional GOP senses that we are at a rare moment of presidential greatness?

Watch: How The Senate Immigration Debate Stalled

Since the Democrats hold a reasonable shot at winning back the House (with the odds going up with the new Pennsylvania redistricting map) and the GOP already faces the indignity of a Democratic senator from Alabama, it is hard to believe that the Republicans see in Trump a path to a permanent congressional majority.

That is, unless the GOP has a secret plan to repeal the 19th Amendment and limit suffrage to white men who watched TV westerns like “Bonanza” and “Wagon Train” during the 1950s.

Many liberals have come to believe that the Republican Party is a burnt-out hulk, devoid of convictions and integrity. But I refuse to accept that a political party (whose prior two presidential nominees before Trump, John McCain and Mitt Romney, were honorable opponents) can morph into a cult of personality that easily.

What I do know is that the Republican excuses for enabling Trump and ignoring his nonstop assaults on decency grow weaker with each passing day — especially since Trump brings to this Faustian bargain neither prudent leadership nor electoral salvation.

When the histories of these dismal Trump years are written, congressional Republicans will be called upon to justify their conduct. Somehow their inevitable line, “It was easier to go along,” will not rank up their with Ronald Reagan’s invocation of “a shining city on a hill.”