A mere week after its election-night triumph, the Republican Party is fracturing more deeply and sharply than anyone had anticipated. Donald Trump’s simultaneous appointments of Republican National Committee Chairman Reince Priebus and alt-right publisher Stephen Bannon—an establishment moderate and a white-nationalist renegade—to co-equal positions set the stage for what promises to be all-consuming internecine warfare in the White House and beyond.

The split is particularly pronounced in the party’s national-security realm, where the latest, clearest—and, to some Republicans, most alarming—sign of discontent is a tweet posted Tuesday morning by a prominent neoconservative scholar named Eliot A. Cohen.

In March, Cohen was a self-proclaimed “ringleader” of a group of 50 former Republican national-security officials who signed a letter in August warning that Trump “lacks the character, values and experience” to be president and “would put at risk our country’s national security and well-being.” Many of the signatories told friends and journalists that, if Trump won and they were asked to join his cabinet, they’d say no.

After Trump won, some of them reconsidered, including Cohen. In a Nov. 11 article posted in the American Interest, titled “To an Anxious Friend,” Cohen wrote that several friends and colleagues had asked him what they should do if Trump offered them a job—and he concluded, with caveats, that they should take it.

“It seems to me,” Cohen wrote, “that if they are sure that they would say yes out of a sense of duty rather than mere careerism; if they are realistic in understanding that in this enterprise they will be the horse, not the jockey; if they accept that they will enter an administration likely to be torn by infighting and bureaucratic skullduggery, they should say yes.” He added, “Each of us has something to offer in restoring a temper of decency, responsibility, and civility to politics. There is plenty of work for all of us to do, and we would do well to get about it.”

Cohen was praised in the Twitter-sphere for his “wise counsel” and public duty. And then came this tweet from Cohen on Tuesday morning:

After exchange w Trump transition team, changed my recommendation: stay away. They're angry, arrogant, screaming "you LOST!" Will be ugly. — Eliot A Cohen (@EliotACohen) November 15, 2016

I should note, I’ve been friendly with Cohen for many years. We disagree on many issues, but I regard him as a serious analyst and wise historian. (His book Supreme Command is one of the best studies of civil-military relations; Military Misfortunes, an edifying analysis of failure in warfare; Conquered Liberty, a surprising and entertaining chronicle of our nation’s early frontier battles with Canada and how they shaped the American way of war.) His annual seminars on military history, taught to officers, have earned him wide respect inside the armed forces’ more intellectual circles. He is sober-minded, sophisticated, not prone to outbursts. In other words, this tweet, in its tone and substance, is uncharacteristic—and for that reason, many of his ilk are taking it seriously.

Cohen told the Washington Post that he’d written the tweet after submitting names for possible national-security positions at the request of a longtime friend who’s a senior official on the Trump transition team. His friend’s response, Cohen said, was “very weird, very disturbing … It became clear to me that they view jobs as lollipop things you give out to good boys and girls.” His friend, he added, seemed “unhinged.”

Max Boot, a senior fellow at the Council on Foreign Relations, and a neocon who signed a similar anti-Trump letter by 122 national-security experts (and agitated against Trump on his Twitter feed until last week), wrote an op-ed for USA Today after the election, arguing—as Cohen did in his American Interest piece—that #NeverTrumpers shouldn’t hesitate to counsel Trump, if just “to save him from himself.” However, when I asked Boot this morning about Cohen’s retraction, he emailed, “Eliot’s tweeting is a matter of concern because it suggests Trump people will stay in their bunker. Heaven help us if they staff the entire admin only with Trump loyalists.”

Another Republican who signed the letter, a former senior official who asked not to be identified, said Tuesday that he too had been encouraging fellow skeptics of Trump to serve if they were called (as long as they weren’t required to renounce their views—“no need for loyalty oaths”), but that Cohen’s email punctured his hopes. Another source of “discouragement,” he said, was the announcement that Mike Rogers, the former chairman of the House Intelligence Committee and before that an FBI agent, had left Trump’s transition team over disputes with the campaign loyalists who seem to be dominating the show.

There is also widespread weariness over reports that the next secretary of state might be Rudy Giuliani, a man with no experience in foreign policy and possibly the least diplomatic personality in American politics, simply because he stood by Trump unwaveringly in good times and bad.

Fasten your seatbelts; it’s going to be a bumpy four years.