Arizona Sen. John McCain on Monday released a lengthy statement rejecting Donald Trump’s pushback against gold star parents Khizr and Ghazala Khan, who have spoken forcefully against Trump since Khizr gave one of the most powerful speeches of last week’s Democratic National Convention. Various prominent Republican officeholders—like House Speaker Paul Ryan, Senate Majority Leader Mitch McConnell, and Trump’s own running mate Mike Pence—have issued terse statements commending the Khans, but McCain’s letter went long.

“I cannot emphasize enough how deeply I disagree with Mr. Trump’s statement,” he wrote. “I hope Americans understand that the remarks do not represent the views of our Republican Party, its officers, or candidates.”

Once he got that necessary grunt work out of the way, McCain moved to more florid ground. He wrote of his family’s own well-known multigenerational connection to the military, and then retold the story of Capt. Humayun Khan’s death in Iraq. “His name will live forever in American memory,” the letter determined, “as an example of true American greatness.” McCain also wrote that he personally “claim[s] no moral superiority over Donald Trump. I have a long and well-known public and private record for which I will have to answer at the Final Judgment, and I repose my hope in the promise of mercy and the moderation of age.” He was simply “[challenging] the nominee to set the example for what our country can and should represent.”

What McCain’s letter did not do, as many observers were quick to point out, was renege on his prior support for Trump’s candidacy. Near the end of the letter, the 2008 Republican standard-bearer urged his 2016 equivalent—with a tinge of threat—to cut the crap. “It is time for Donald Trump to set the example for our country and the future of the Republican Party,” he wrote. “While our Party has bestowed upon him the nomination, it is not accompanied by unfettered license to defame those who are the best among us.”

So far, Trump has accused Khizr Khan of suppressing his grieving wife from speaking because of some unknown Muslim code, said Khan had “no right” to criticize Trump, and went after Khan on Twitter. What sort of action, exactly, does Trump need to take for McCain to withdraw his blessing? Does Trump need to straight-up punch the Khans in the face? Does Trump need to punch McCain himself in the face?

It’s unlikely that McCain will ever drop his endorsement. If he does do it, though, it would almost certainly come after Aug. 30—the date of Arizona’s Republican Senate primary.

There are reasons beyond the completely cynical and personally craven for McCain to support Trump. As Republicans, they agree more than they disagree. As a Republican legislator, McCain would like to have a Republican partner in the White House. McCain would also not like conservatives to lose their Supreme Court majority, and McCain wants to respect the will of Republican primary voters.

But perhaps more urgently, McCain would not like to lose own re-election this year. As I wrote in July, McCain faces both an underdog challenger, former state Sen. Kelli Ward, in that primary later this month and a well-funded Democratic challenger, Rep. Ann Kirkpatrick, as a potential opponent in November’s general election. Border-state Arizona Republicans are a Trumpy lot, and McCain needs to appease conservatives in the primary and then ride them to victory in the fall.

November remains the bigger challenge for McCain, but one development this weekend just made the primary less comfortable. Alex Meluskey, a businessman who was running in the primary and drawing a healthy chunk of the anti-McCain vote away from Ward, suspended his campaign on Sunday. The timing of this is perfect for McCain’s rival, coming just a few days before early voting begins. Meluskey had been diluting the opposition to McCain, and some conspiratorially minded conservatives—like, for example, Ward herself—thought that Meluskey might have been on the take from the McCain camp. If he was, the payments must have stopped.

“Today Alex Meluskey has honored his pledge to Arizona Republicans ‘to clear the way for the defeat of John McCain,’ ” Ward said in a statement Sunday. “I thank him for his selfless and courageous decision …”

There is still another primary challenger in the race, Clair van Steenwyk, a regular protest candidate who may snag a few percentage points for himself. But the Arizona Republican Senate primary just got a lot closer to the head-to-head race that Ward wants with McCain. It would still be a shock if she “retires John McCain,” as she aspires to do. She would have a much better chance if McCain, right now, made a big show of rescinding from Trump his cautious endorsement. And that’s the main reason why it’s not happening.

That’s not going to stop Ward from trying to use this letter against McCain. “The Khan controversy is a cynical political stunt cooked up by the Clinton Establishment, and, sadly, John McCain has fallen right into it,” Ward said in a statement Monday. “McCain’s statement today makes clear that he really wants Hillary Clinton in the White House, and his tepid ‘support’ for Trump is only disingenuous pandering.” The statement went on to “sympathize” with the Khans for the loss of their son, an “American hero,” before switching back to Trumpian red meat:

However, the Khan’s anger should be directed against those who sent their son into an unnecessary war, like Hillary Clinton and John McCain whose reckless policies and fuzzy Utopian ideals have destabilized the Middle East and triggered a massive refugee crisis, which they want to import into the U.S. to fatten up the welfare rolls.

McCain did not attend the Republican National Convention. He and his aides could watch it on television, though, and surely they noticed the hostile reaction Sen. Ted Cruz met when he refused to endorse Trump in his speech. McCain, like others up for re-election in the party, need to keep Trump at arm’s length when he pops off, as he is known to do. But McCain can’t afford to position himself in total opposition to the nominee, just as the state begins to vote on whether he’ll get a chance hold onto his seat in the fall.

Read more Slate coverage of the 2016 campaign.