With the first Republican debate looming on August 23 at Milwaukee, the party ought to be steaming toward next fall’s showdown with an unpopular incumbent, President Biden. Instead, the event is devolving into a chaotic exercise in herding cats.

The 2016 Republican debates featured almost 20 candidates, resulting in a main stage and the so-called “kids table.” This year, the Republican National Committee sought to constrain the field by imposing fund-raising requirements and a one percent showing in three national polls, as well as extracting a commitment to support the eventual nominee.

These requirements may ace out those like Vice President Pence, whose resume would have guaranteed him a slot in years past, and the former governor of New Jersey, Chris Christie, who has balked at the pledge and is struggling to amass the 40,000-strong donor list to qualify for what he sees as a make-or-break event.

“I think for those people who don’t make the debate stage,” Mr. Christie told Politico, “it’s very hard for them to make the case for why they should stay in the race, and I suspect they will have trouble raising money after that.”

Only President Trump, Governor DeSantis of Florida, Ambassador Nikki Haley, Senator Scott of South Carolina, and Vivek Ramaswamy have reached the required number of donors, which the RNC says must be drawn from a minimum of 200 unique individuals in 20 states.

Mr. Trump — who says he disapproves of the format and of host Fox News Channel, which he described as “a hostile network” to Reuters — is roiling the waters by playing Hamlet on whether he’ll attend at Milwaukee or the second debate at the Ronald Reagan Presidential Library in California.

On Telegram, Mr. Trump floated counter-programing the first debate by hosting a separate event, as he did in 2016 before the Iowa Caucuses, by hosting a fundraiser with veterans instead. This year, he has even more incentive to take his ball and go home again rather than suffer the slings and arrows of his opponents.

“Why would I give them time to make statements?” Mr. Trump asked Reuters. “Why would I do that when I’m leading them by 50 points and 60 points?” It’s the same rationale the incumbent, President Biden, is using to avoid debating Democratic challenger Robert F. Kennedy Jr.

With the nomination looking like Mr. Trump’s to lose without the sort of major stumble a debate might provide, the RNC is further complicating matters by requiring candidates to sign the loyalty pledge, which the crowded field interprets as a commitment to support Mr. Trump.

Mr. Trump signed such a guarantee in September 2015 at the behest of the party chairman, Reince Priebus, but abandoned it six months later. While it was moot in the end, candidates trying to separate themselves from the former president may not wish to repeat what they see as his duplicity.

“I think the pledge is just a useless idea,” Mr. Christie said on CNN, citing the fact that in a 2016 debate, the 10 candidates were asked to raise their hands to reaffirm the pact and only nine did. “The one who didn’t was Donald Trump.” It’s a strong retort, one he may not get the chance to make on stage.

“I’m gonna work towards hitting all the requirements,” a former Republican member of the House, William Hurd, told CNN of the pledge, “but I can’t lie to get access to a microphone.” He has taken one oath, he said, “and that’s to protect the Constitution,” he said. “I’m not going to support Donald Trump.”

A former governor of Arkansas, Asa Hutchinson, also balked, suggesting “a little rationality” and asking that the RNC amend the pledge because he would not vote for “a convicted felon” or someone “convicted of espionage” or “other serious crimes.” His request was rejected.

Instead of debates that put the GOP’s best foot forward and focus on unseating Mr. Biden, Republicans are on track for chaos with some of their strongest candidates refusing to be herded onto stage — chaos that can only benefit Mr. Trump and ensure that he, once again, emerges from the primaries as top cat.