Sen. Ted Cruz, R-Texas, issued a blistering and accurate attack on Donald Trump in the waning days of Cruz's presidential race in May. He nailed him as a "pathological liar" and spotted his dangerous narcissism. He excoriated Trump for insulting his wife and accusing his father of being connected to the JFK assassination.

At the the Republican National Convention in July, Cruz chose to show up — and pointedly did not endorse Trump. He was booed robustly but earned some grudging admiration from sincere conservatives. "To those listening, please, don't stay home in November," Cruz said. "Stand up and speak and vote your conscience, vote for candidates up and down the ticket you trust to defend our freedom and be faithful to the Constitution." That lasted about two months.

Naturally then, Cruz endorsed Trump on Friday on his Facebook page.

What?!

No, there is no rational explanation. Everything Cruz listed as a justification for voting for Trump — the Supreme Court, for example — was a concern in July. Trump, if anything, has become more accustomed to lying (e.g., accusing Hillary Clinton of starting the birther lie). It's obvious to Trumpkins, #NeverTrump Republicans, the media, Democrats and every voter in Texas that Cruz simply lost his nerve, got concerned he would be accused of sinking Trump and couldn't bear the estrangement for the tea party faction that largely supported him in the primary.

The reaction on his Facebook page ranged from horrified to furious. One person wrote, "What's sad is you actually sound like the exact opposite person as you did in the debates, on the campaign trail, on convention night and the days since."

Another said: "You have to be kidding me. What a sellout. I am ashamed to have supported you. By endorsing him you are endorsing everything he has said about you and so many others. What happened to, 'I'm not in the habit of supporting people that attack my wife and my father'? You are endorsing his liberal policies and the destruction of the conservative portion of the Republic Party. You just lost a voter, Mr. Cruz. The last standing conservative has bent his knee to the liberals running this country into the ground."

Oof.

Reaction from conservatives in the media was brutal. "So long as Trump's proposals can be defended as somewhat more right-wing than what Clinton would give us, that's conservative enough. If that's the guy Cruz is now, he'd better never open his mouth to criticize Mitch McConnell again," wrote Allahpundit. He continued, "The core argument against Trump is that he's unfit for office in terms of qualifications, temperament, and basic morals. He's a con artist, like fellow Trump endorser Marco Rubio said. And the key point here is that Cruz himself has made that argument."

Ana Navarro, a Jeb Bush supporter, referred to Trump's insults directed at Heidi Trump. "If after saying he was standing up for my honor, my man endorsed a guy who called me ugly ... he'd be sleeping on the damn couch for months," she wisecracked.

And David French, who contemplated an independent conservative run, ridiculed the notion that Cruz could not stand up to "pressure." French wrote, "What pressure? You might get primaried? The terrifying Reince Priebus might get angry? You might *gasp* lose your Senate seat? Good heavens — the nation just can't survive without Cruz in the Senate!"

In caving just after Priebus announced he would make it hard for those who signed the pledge to run, Cruz looks like a coward — the only person on the planet afraid of the RNC chairman. Whatever advantage he had over other Trump supplicants like Sen. Marco Rubio, R-Fla., has evaporated. The Texas Monthly was blunt:

"Either his endorsement is a pack of lies, or his speech at the RNC was: They can't both be true. And though it's possible that 'Lyin' Ted' might still one day become president, the odds, in my view, are now vanishingly narrow. We've all heard it a million times: 'Everyone hates Ted Cruz.' And now he's given this faceless 'everyone' plenty of reason to do so."

Cruz's move is nearly inexplicable. In the vein of the "Jeb!" motto in the campaign, Cruz's endorsement amounts to "Opportunist!" or maybe "Coward!" Cruz is in the business of accusing every other Republican of selling out to big government liberals. Now he has done the same in embracing the big government nominee.

"While Ted Cruz isn't the first to betray our country's interests in exchange for political expediency, he is certainly one of the most important," said independent conservative candidate Evan McMullin in a written statement. "It's why the GOP is in such deep trouble as a political vehicle for the conservative movement and for American leadership. "

As many of his critics have observed, Cruz is not, as he claims, all about putting conservative ideals above blind party loyalty. It is and always has been about Cruz. Unfortunately, he has made that so obvious as to become the butt of Republican jokes. That scorn is richly deserved.

Jennifer Rubin writes the Right Turn blog for The Post, offering reported opinion from a conservative perspective.