Ted Cruz set aside his many differences with Donald Trump on Friday to endorse for president a man whom he once called a “serial philanderer,” a “pathological liar,” “utterly amoral,” and a “sniveling coward”; who insulted his wife’s looks; who insinuated Cruz’s father was involved in the assassination of John F. Kennedy; who said he wouldn’t even accept his endorsement; and who for months mocked him mercilessly with a schoolyard taunt, “Lyin’ Ted.”

The Texas senator announced his support for the Republican nominee late Friday afternoon in a Facebook post, writing that the possibility of a Hillary Clinton presidency was “wholly unacceptable” and that he was keeping his year-old commitment to back the party’s choice. Cruz listed six policy-focused reasons why he was backing Trump, beginning with the importance of appointing conservatives to the Supreme Court and citing Trump’s recently expanded list of potential nominees. Other reasons included Obamacare—which Trump has vowed to repeal—immigration, national security, and Trump’s newfound support for Cruz’s push against an Obama administration move to relinquish U.S. oversight of an internet master directory of web addresses.

“These are six vital issues where the candidates’ positions present a clear choice for the American people,” Cruz wrote. “If Clinton wins, we know—with 100% certainty—that she would deliver on her left-wing promises, with devastating results for our country. My conscience tells me I must do whatever I can to stop that.”

Yet if there are six reasons Cruz gives for embracing Trump, there are another five for why his endorsement is the most stunning about-face of any of the Republicans who once opposed the real-estate tycoon.

Words No Longer Matter

The examples at the start of this article are just a small sample of the vitriol exchanged between Cruz and Trump during the height of their primary battle. Yes, Trump exchanged insults with just about all of his Republican opponents, and many of them—like “Little Marco” Rubio—ended up endorsing him. But Cruz is now backing a man for the nation’s highest office that he considers to be a liar, a coward, and amoral. Those are charges you don’t just take back or minimize, and to do so reinforces the cynicism that many voters have about the political process.

Honor Thy Father?

Cruz had a pretty good reason for calling Trump all those things back in the spring: Trump ran an astonishingly dirty campaign against him! Just as he did for years with President Obama, Trump repeatedly floated a birther theory about Cruz and suggested he was ineligible for the presidency because he was born in Canada. He even threatened to sue Cruz over it. Then Trump turned on Cruz’s family. He tweeted unflattering pictures of Cruz’s wife and threatened to “spill the beans” on her (though he never hinted at what “the beans” entailed). Finally, Trump spread a rumor, based off a grainy photo in the National Enquirer, that Cruz’s father Rafael was involved in the Kennedy assassination—and he continued raising it the day after he accepted the Republican nomination for president. Cruz didn’t mention this in his Facebook post, presumably lumping all of these charges into the “significant areas of disagreement” that he acknowledged he has with Trump.

Brand Ruination

Cruz has worked diligently over the years to forge a political identity that can be summed up thusly: He is a conservative who fights on principle, whether or not that accords with the wishes of his party’s leadership. By bowing down to a man he has attacked so harshly, Cruz significantly dilutes that brand. As I wrote previously, Cruz is facing a potentially difficult primary battle in his reelection bid for the Senate in 2018, and he undoubtedly determined that he needed to make amends with the sizable contingent of Trump supporters in Texas—especially knowing that he can’t count on the support of party leaders he has long since alienated.

Polls showed Cruz’s support among Republicans dropped significantly when he refused to endorse Trump at the GOP convention in Cleveland. Yet conservatives, including some of Cruz’s top allies and former advisers, are already calling this decision just as self-serving as that one. As for whether Cruz’s political calculations help or hurt him if he runs for president again in 2020, it’s surely too early to say. Cruz now leaves Ohio Governor John Kasich as perhaps the most Trump prominent holdout who is eyeing another White House bid in four years.

What About Cleveland?

One of the more curious aspects of Cruz’s endorsement is the timing. If he was planning to honor his commitment to support the Republican nominee, why did he make a dramatic show of snubbing Trump at the convention in Cleveland, when instead of endorsing him he urged delegates and the public to “vote your conscience”? Former rivals like Rubio faced a similarly difficult choice, but they were all able to issue their muted, stilted endorsements with less fanfare and less waffling.

Promises, Promises (Trump Doesn’t Keep ’Em)

The policy reasons that Cruz cites are all based on promises Trump has made, including his two separate lists of potential Supreme Court appointments. Yet as Cruz himself has pointed out, Trump is never more slippery than when it comes to policy. He has already revised his tax plan and his infamous call to bar Muslims from entering the United States, among many other examples. Why should Cruz trust Trump on any of his other pledges? Within minutes of Cruz’s statement Friday, Trump added yet another flip-flop. Two months and one day ago, Trump said point-blank regarding the possibility of a Cruz endorsement: “If he gives it, I will not accept it.” By Friday, he apparently changed his mind. “I am greatly honored by the endorsement of Senator Cruz,” Trump said in response.