On the eve of the presidential election in late October 1964, Ronald Reagan pleaded with voters to “preserve for our children this, the last best hope of man on Earth” by voting for Barry Goldwater, rather than “sentence them to take the last step into a thousand years of darkness.” His speech was called “A Time for Choosing,” and a few days later voters chose to deal Goldwater a huge, embarrassing, landslide defeat. Nevertheless, things worked out okay enough that 20 years later (just 980 off the mark), Reagan was able to declare it morning in America.

From the early days of this year’s presidential primary, Ted Cruz deployed Reagan’s failed entreaty repeatedly—always to imply that his opponents have failed the public somehow. The aftermath of President Obama’s reelection was, in Cruz’s telling, a time for choosing, and Marco Rubio disgracefully chose amnesty. More recently, Cruz described Tuesday night’s Indiana primary as a “time for choosing,” suggesting that those who chose Trump over him would be welcoming the darkness.

Cruz’s plea worked about as well on his own behalf as Reagan’s did on Goldwater’s. Trump demolished Cruz in Indiana, leaving no doubt that he will win the Republican presidential primary on the first ballot in Cleveland two months from now. News networks called the race for Trump the moment polls closed in Indiana, and an hour-and-a-half later, Cruz ended his campaign.

He delivered his concession speech with an eye toward the future of conservatism—a movement he offered to lead—but was silent on the near-term, and conspicuously omitted two words: Donald Trump.

That means a time for choosing is now, fittingly, upon Cruz—along with a whole array of conservatives who have either vowed to oppose Trump’s candidacy through November, or who’ve implied in their critiques that Trump is unfit for office. Their decisions will help determine what the Republican Party looks like after Trump, and whether the conservative movement comes out of the 2016 election diminished or extinct. And nobody’s choice will matter more than Cruz’s.

Cruz has never been explicitly in league with the #NeverTrump camp. While many skeptical Republicans have left themselves plenty of room to support Trump in the general election without contradiction, Cruz has walked right up to the #NeverTrump line, without ever quite crossing it.

In March, after Trump launched a sustained attack on Cruz and his wife Heidi, the Texas senator delivered an ultimatum of sorts, saying, “I don’t make a habit out of supporting people who attack my wife and attack my family,” which either means he will oppose Trump or will make a one-time exception to the family-honor rule. A month earlier, Cruz had intimated that Trump might be reluctant to release his tax returns because they’d reveal his “business dealings with the mob, with the mafia.” And for weeks now, he has claimed, rather desperately, that Trump is essentially no different than Hillary Clinton—“Behind the Donald Trump mask is Hillary Clinton”—raising the question of what difference it makes whether Republicans back Trump, Clinton, or nobody.

On Tuesday, as Indiana Republicans were going to the polls, Cruz prefaced a comprehensive attack on Trump by effectively admitting that his own previous Trump comments were either disingenuous (for instance: “@realDonaldTrump is terrific”), or that he had been pulling his punches in his critiques. “I’m going to do something I haven’t done for the entire campaign,” he said. “I’m going to tell you what I really think of Donald Trump.”

This was likely the first tirade in the modern history of American political combat to address a rival’s supposed “battles with venereal disease.” Cruz delivered it knowing it would be his last word on Trump before ceding the nomination to him. He also knows that at some point in the next several weeks, he will have to choose between his conservative values and his partisan obligation to help someone he just called “amoral” and a “pathological liar” become the president of the United States.

Other conservatives have paved the walk of shame for Cruz, should he decide to fall into line. Weeks after calling Trump a con man, and saying the thought of supporting Trump in the general election was “getting harder every day,” Rubio said Trump’s “performance has improved significantly,” and suggested he will help unite the party if Trump wins the GOP nomination.

But Cruz’s shame would be greater still. Cruz has gone out of his way to say that he withheld his true assessment of Trump until the ultimate moment for choosing. That assessment is more unsparing than any Republican’s criticism of Hillary Clinton, let alone of Trump himself. And as a leader of the conservative movement, Cruz’s loyalties are more divided than just about any of his fellow partisans’.

Cruz’s options are uniquely terrible. His best bet may be to escape the public eye until November, in the hope of saying, I told you so.

If Cruz decides to lead a conservative splinter party, or a loyal-but-vocal Republican opposition, it’ll allow the Trump faction to spin up a stabbed-in-the-back story about why the GOP nominee lost in November, and thus make uniting a single post-Trump party of the American right impossible.

In any case, as #NeverTrump morphs into #EventuallyTrump, the power and prestige of the existing conservative movement will drain away, along with the logic and allure of leading an anti-Trump resistance.

That will make it tempting for Cruz to cozy up to Trump. But if he does, he would take everything that he claimed distinguished him from the Republican establishment and flush it down the toilet. By what consistent principle can a man who shut the government down in hopeless protest of Obamacare turn around and endorse someone who’s supposedly Hillary Clinton with a penis?

Cruz has, throughout his brief political career, shown an amazing facility for building himself up at the expense of other Republicans. His following remains real, and probably large enough that if Trump weren’t practically destined to lose the general election anyhow, he could deny Trump the presidency all on his own simply by refusing to back him.

If anyone has the blind ambition required to oppose his own party’s presidential nominee, hoping it will pay professional dividends in the future, it is Cruz. Conservative intellectuals have been by-and-large suspicious of Cruz’s tactics and motives all along, precisely because of that overwhelming ambition. But to the extent that they take their Trump opposition seriously, Cruz has perversely become their best hope for enduring influence over politics. And if Cruz eventually makes his peace with Trump, then movement conservatism will be well and truly dead.

For more on the 2016 elections, take a listen to our podcast, Primary Concerns, hosted by Brian Beutler: