Why don’t Republicans stand up to Trump? Here’s the answer.

If you’re still flummoxed by the abject servility of congressional Republicans, by their refusal to confront Trump and stand up for American values, check out last night’s primary election in South Carolina. The purging of Mark Sanford says it all.

Sanford is a long-serving conservative lawmaker (and former governor) who typically votes with his party, but on a few public occasions, he has actually dared to suggest (gasp) that Trump is not the supreme very stable genius that the deluded Republican base deems Trump to be. The result: Sanford loses his job.

For the inexcusable sin of speaking his mind about factual reality, the Republican base voters in Sanford’s House district threw him out last night, handing the GOP nomination to a far-right Trumper who repeatedly denounced Sanford as “disloyal.”

This is why rank-and-file Republican lawmakers refuse to speak out. They’re afraid of their own constituents. It’s Trump’s party now, and the constituents in red districts virtually worship the guy. Forget about putting country over party, because it’s actually worse than that. Sanford’s colleagues won’t put country over career. They’ll vow that what just happened to Sanford will not happen to them.

As conservative commentator Erick Erickson said today, “Mark Sanford losing in South Carolina is pretty much proof positive that the GOP is not really a conservative party that cares about limited government. It is now fully a cult of personality.”

What did Sanford say that was so blasphemous? For starters, he told reporters during the ’16 campaign that Trump had somewhat shaky knowledge about the U.S. Constitution. After Trump met with House Republicans to showcase his wisdom, Sanford actually said: “I wasn’t particularly impressed. It was the normal stream of consciousness that’s long on hyperbole and short on facts. At one point, somebody asked about Article I powers: What will you do to protect them? I think his response was, ‘I want to protect Article I, Article II, Article XII,’ going down the list. There is no Article XII.”

Trumpists don’t like fact-checkers, because the party line is that Trump is never wrong.

Sanford also made the mistake of publicly calling on Trump to release his tax returns, just like every other candidate and president had done since 1976. He refused to echo Trump’s promise that Mexico will pay for a border wall. He also said that Trump’s nascent international trade war – specifically, his proposed tariffs on foreign aluminum and steel – is “an experiment in stupidity.” He also said that Trump’s remark about “shithole” African nations was “stupid.” But Trumpists don’t like it when Trump is called stupid, because the party line is that Trump is always wise.

Sanford actually saw this day coming. A month after the ’16 election, he said of his Republican colleagues: “People are naturally reticent to be the first out of the block, for fear of Sean Hannity, for fear of Breitbart, for fear of local folks.” And frankly, yours truly saw his day coming. On Dec. 21, 2016, I wrote:

“This is how democracy ends and autocracy begins – with lawmakers terrified to speak freely, lest the tweeting Trumpkins and alt-right propagandists lay siege to their souls…We need to understand how profoundly our politics are about to change. We need to understand that the congressional members of the ruling party will soon be under the heel of Trumpthink, and that their fear of reprisal will likely keep them in line. They won’t need to wear T armbands. The chilling effect, and their cowed silence, will be sufficient.”

I stand by every word.

Sanford is the second House Republican in recent weeks to suffer for refusing to be silent. In Alabama, Martha Roby may yet survive, but in a recent primary she failed to clear 50 percent of the vote. Under Alabama rules, she has been forced into a July 17 runoff against a lockstep Trumpist. Roby’s sin, despite her conservative track record? Two years ago, after the release of Trump’s “Hollywood Access” remarks about women, she said that Trump was “unacceptable as a candidate for president.” (Gee, I can’t imagine where she got that idea. But she could lose her job for voicing it.)

So most Republicans will remain in a fetal position unless or until the Republican base abandons Trump. But don’t bet on that happening. I get emails all the time from base inhabitants, and they read like rote chantings from Chairman Mao’s Little Red Book.

In fact, I got one yesterday from a fellow citizen in Georgia: “Donald Trump is a phenomenon that most foreign countries have never seen before and he gives us a new understanding about foreign policy and will certainly achieve tremendous success…He is one true leader and is a man who is making changes like never before and is doing this for the sake of this nation’s people. After eight years of Obama’s tyranny, we are at last finally seeing a difference…Something remarkable and new is emerging.” And so on.

As for Mark Sanford, he conceded defeat last night with these words: “I stand by every one of those decisions to disagree with the president.” But rest assured, his chastened colleagues have gotten the message that disagreement spells doom.