In July of 2015, Donald Trump went out of his way to insult Sen. John McCain, insinuating that he was a loser because he spent five years as a prisoner of war under the Vietcong. Many people have forgotten about that because, frankly, that was about a thousand Trump scandals ago.

But Jeff Flake, Arizona’s junior senator and one of the Grand Old Party’s harshest critics, has not forgotten.

It should be noted that Sen. McCain himself has endorsed Trump — however tepidly — choosing instead to focus on his tough upcoming reelection race against Rep. Ann Kirkpatrick.

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Flake, on the other hand, personally took Trump to task during the candidate’s visit with Republicans on Capitol Hill this July. He introduced himself as the Arizona senator “who didn’t get captured” and went on to pointedly miss the Republican National Committee because he had to mow his lawn.

Still, nothing beats the excuse Republican Sen. Ben Sasse of Nebraskaused for missing the convention, which heavily implied that taking his children to watch dumpster fires was a preferable activity to watching Trump assume his party’s mantle.

In any event, the question must be asked: Why such vocal opposition? Republican Rep. of Wisconsin and Speaker of the House Paul Ryan is clearly not overjoyed that Trump is his party’s nominee, but even he bit the bullet and endorsed the billionaire.

For historical precedent, look at Richard Nixon’s behavior during the 1964 presidential election. Arizona Sen. Barry Goldwater was the GOP’s nominee, and his prospects were awful. His own outlandish comments —“extremism in the defense of liberty is no vice”— and then President Lyndon B. Johnson’s strength seemed to many Republicans to be sure signs of a landslide Democratic victory.

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Nixon was one of those Republicans, and he nonetheless campaigned for Goldwater until the bitter end, because it positioned him well for the future, according to Michael A. Cohen’s, “American Maelstrom,” and Joe McGinniss’, “The Selling of the President.”

You could point to the future president and say, “That Nixon guy, he’s a hell of a party man.”

That’s not the route Flake is taking. He has positioned himself publicly and privately as the man taking a moral stand against Trump. His outspokenness also highlights his colleague’s relative silence on the matter.

It’s disappointing — if not surprising — that McCain has followed party diktat so closely. His unenthusiastic endorsement of the GOP candidate — based on the argument that the people have chosen their candidate — makes sense given that the negative press he would get for dumping Trump would likely hurt his reelection campaign.

But what happened to the maverick? This is still the man who resolutely did not follow the party line when he voted against Ronald Reagan’s deployment of U.S. troops in Lebanon. 

This is still the man who refused to follow common sense when he okayed the addition of Sarah Palin, the human equivalent of a misfired Patriot missile, to his ticket in 2008.

His junior counterpart has perhaps out-mavericked him. For all his flaws — and there are many — Flake has displayed remarkable moments of courage and principle.

He traveled to Cuba with President Barack Obama, and just this summer supported a gun control bill  — that failed.

In a proud moment for Arizona politics, he spoke at a mosque in Scottsdale after the shooting in San Bernardino, California and offered words of support to the Muslim community, as well as words of condemnation for the New York real estate mogul.

Maybe McCain and Flake are two sides of the same coin. McCain is thinking tactically, and Flake strategically as he looks ahead toward his uncertain political future.

Maybe Arizona has produced a flawed-but-principled politician who could just not abide the disrespect and violence that Trump preached and continues to preach.

A good litmus test will manifest in the next few week as Trump makes half-hearted attempts at looking presidential (like his recent blimp crash of a visit to Mexico). If those kinds of hollow pieces of carnival showmanship are enough to convince Flake, any attempts to describe him as principled will be futile.

However, if Flake holds his ground, as McCain might have in a different year, Arizonans can take pride in a senator who stood up, for better or worse.

Follow Raad Zaghloul on Twitter.