During the July 4 holiday weekend, my daughter texted me a selfie from the Connecticut coastline where she was visiting a friend’s family. At first, I could not fathom the image. Here was my 22-year-old, a Hillary Clinton supporter from a family of fervent Democrats, smiling with another vacationer on Fishers Island: The right-wing Republican senator and recently defeated candidate for the presidential nomination, Ted Cruz.

By now, three weeks later, I consider that snapshot a strange kind of presentiment for the entirely unexpected role Cruz has played in clarifying the stakes in this campaign and the starkly dangerous role Trump has in it. The provocateur behind a government shutdown in 2013, the advocate of anti-Muslim and anti-immigrant positions nearly as extreme as Trump’s, a favorite of zealots in the Christian Right and the National Rifle Association, Cruz has stunned the American public by becoming the least likely hero.

His heroism is all the more confirmed by the hatred he has received from Trump’s convention clones, who booed the Texas senator off the stage, as well as more traditional conservatives who wanted him to obediently close ranks on the theory that Hillary Clinton is somehow a greater threat to the republic than the American version of Mussolini.

Cruz’s perfidy, of course, consisted of refusing to endorse Trump while addressing the Republican convention, contravening a written pledge all 17 Republican candidates had signed months ago. Rationally enough, amid a Republican race short on rationality from its frontrunner, Cruz contended that such a pledge was overridden by Trump’s scurrilous attacks on the senator’s wife (for her appearance) and father (for consorting with Lee Harvey Oswald in the JFK assassination).

Those comments by Trump typified his rhetoric of innuendo, fabrication, and personal insult throughout the entire primary campaign. The journalist and author Jim Sleeper has written of a societal compact he calls “a standard of public truth.” It delineates, among other things, the difference between aggressive, even slanted attacks on a political rival and outright trafficking in lies and conspiracy theories.

Trump’s campaign of racism, nativism, misogyny, Islamophobia, anti-Semitism, and mockery of the disabled – in sum, identity politics for white nationalists – has depended on several Big Lies. He claims violent crime is rising when it has been demonstrably falling for 25 years. He claims illegal Mexican immigrants are invading the nation even though the numbers of departures actually exceeded arrivals from 2009 through 2014. He espouses a ban on Muslim immigration that would instantly alienate an existing Muslim-American population that, despite several lone-wolf terror attacks, is a model of moderation and assimilation for the entire world.

Yet many of those positions sounded similar enough to the red meat tossed to the mob by other Republican candidates that it didn’t force a reckoning with what Trump embodies. Yes, to their credit, former presidents George H.W. Bush and George W. Bush, former presidential nominees John McCain and Mitt Romney, and this year’s also-rans Jeb Bush and John Kasich refused to attend the convention.

But it took Cruz’s prime-time, televised snub – that punch in the face every bully deserves and all too few ever receive – to carve a defining divide in the electorate. This chasm separates not Democrats and Republicans or liberals and conservatives. It separates the hateful and ignorant from the decent.

It helps to be constantly reminded of Trump’s toxicity, which combines the groundless insinuations of the Red-baiting Joe McCarthy with the demagogic magnetism of the segregationist George Wallace. Here is a portion of what Trump said, the morning after he was nominated, regarding Cruz’s father:

“All I did was point out that on the cover of the National Enquirer there was a picture of him and crazy Lee Harvey Oswald having breakfastThis was a magazine that frankly, in many ways, should be very respectedNow, I’m not saying anythingIt had nothing to do with me.But nobody every denied – did anyone ever deny it was his father?”

In the community of conservative Republican Jews, figures such as William Kristol, Elliot Cohen, David Frum, Jonah Goldberg, Bret Stephens, and David Brooks have admirably rebuked Trump. They are not willing to take the whole despicable package for a few pandering talking points about tearing up the Iran deal and using the phrase “Islamic terrorism.”

But Sheldon Adelson, whose fortune calls many tunes both in America and Israel, pointedly refused to meet with Cruz after the non-endorsement speech. Adelson has pledged $90 million to Trump’s general-election campaign. A recent article by Jonathan Mark in the New York Jewish Week had Jewish Trump supporters crying crocodile tears about how unfair criticism of them was. There has been a backlash of support for Rabbi Haskel Lookstein after he was rightfully shamed into withdrawing from a role giving the invocation on the convention’s opening night.

As even Ted Cruz understands – and this is Ted Cruz, the most extremist Republican in the Senate – this election is not partisan business as usual.

Samuel G. Freedman is the author of eight books including “Jew vs. Jew: The Struggle for the Soul of American Jewry.” Follow him on Twitter: @SamuelGFreedman