President-elect Donald Trump’s bid to stock his Cabinet with combative loyalists is creating the first major test for the new Senate Republican majority, whose leaders must now decide how far they are willing to go to challenge nominees some of them regard as egregiously unfit.

The issue reared its head only hours after Sen. John Thune, R-S.D., won the post of majority leader. Trump then announced he was choosing Rep. Matt Gaetz, R-Fla., who was under investigation, but never charged, over sexual misconduct with minors and illicit drug use, to be attorney general. The next day, Trump announced that he had chosen Robert F. Kennedy Jr., a vaccine skeptic, to lead the Department of Health and Human Services.

Lawmakers were already reeling at Trump’s plans to nominate Fox News host Pete Hegseth as defense secretary and former Rep. Tulsi Gabbard of Hawaii, who has been accused of promoting Russian propaganda, as director of national intelligence.

Now Thune, who will officially assume his post in January, must balance the deep misgivings among his rank-and-file with Trump’s demands of fealty, and habit of punishing those who dare to cross him. The president-elect’s threat to use recess appointments to unilaterally install nominees who cannot clear the Senate otherwise has deepened the conundrum, holding out the possibility of a constitutional clash at the outset of Trump’s second term.

So far, Thune, who was elected over a challenger more closely aligned with Trump, has studiously avoided opining on any of the candidates. Many Republicans said they were inclined to defer to Trump on all but the most outrageous nominees — some of them naming Gaetz as beyond the pale. But some Republicans said a confrontation could be coming if Trump tried to go around the Senate to appoint a slew of unacceptable candidates through recess appointments.

“I think all but Gaetz are very doable — maybe not lovable, but doable,” Sen. Kevin Cramer, R-N.D., said in an interview conducted before Trump’s announcement about Kennedy.

But if Trump tried to undermine the Senate’s role by forcing the chamber into recess so that he could circumvent its vetting, “this is where we stop — this is the end of the bridge,” Cramer said. “Everything else I can get on board with. I can make the case for the rest.”

Democrats, most of whom are expected to oppose Trump’s nominees, said they were facing even more existential stakes given the Senate’s role, laid out in the Constitution, of evaluating and confirming presidential nominees.

“It’s certainly a test of whether they are going to provide any independent check on the president and his plans to weaponize the Department of Justice for political purposes,” Sen. Christopher S. Murphy, D-Conn., said, adding: “If we just give up on confirmations because Trump asked, that’s the end of the Senate.”

Publicly, Thune and other Republican leaders have adopted a stance that has become a sort of mantra: Trust the confirmation process to sort everything out.

“We don’t know until we start the process, and that is what we intend to do with him and all the other potential nominees,” he told reporters Thursday, when asked about Gaetz’s candidacy.

“The president’s going to make his appointments; we’re going to continue to look forward to them coming to the Senate, and have hearings, and get his Cabinet in place,” said Sen. John Barrasso, R-Wyo., who was elected Wednesday to be the No. 2 leader in the next Congress.

But Republicans are split over how deeply the Senate ought to probe Trump’s picks — particularly Gaetz.

On Thursday, Sen. John Cornyn, R-Texas, said that he “wants to see everything” on Gaetz, including a pending House Ethics Committee report. The panel’s investigation of Gaetz effectively ended when he abruptly resigned from the House on Wednesday.

Cornyn said he would favor issuing a subpoena if the panel did not turn its unreleased report over to the Senate willingly.

“I don’t think any of us want to fly blind,” Cornyn said. “Part of this is to protect the president against information or surprises coming out later that he and his team weren’t aware of.”

That could also lead to a constitutional clash between the two houses of Congress.

“I would not like them to subpoena something from us,” said Sen. Lindsey Graham, R-S.C.

Graham is one of the few GOP senators who has spoken favorably about Gaetz’s nomination. On Thursday, he also signaled he would support Gabbard — even though he is a foreign policy hawk deeply critical of Russia, and Gabbard has a track record of promoting conspiracy theories backed by the Kremlin.

“We’ll see how she does, but I like her,” Graham said. “We have our disagreements.” He added: “I generally defer to presidential picks. I’ve done it in the past; I’ll probably do it again.”

Some Republicans were clearly struggling this week to muzzle their disdain for Trump’s choices.

“I think it would be responsible for me to learn more about each of these nominees with whom I am not particularly well acquainted,” Sen. Todd Young, R-Ind., told reporters when asked about Gabbard. He then urged reporters to look at his social media feed, where he has praised many of Trump’s choices — but noticeably not Gabbard, Gaetz or Hegseth.

“He’s got his work cut out for him,” Sen. Joni Ernst, R-Iowa, said when asked about Hegseth potentially becoming defense secretary. Several senators have raised concerns that Hegseth’s lack of management experience could be a liability atop the behemoth Pentagon; Ernst was also thought to be on Trump’s shortlist for the job.

Many others appeared equally tortured as they tried to be diplomatic about Trump’s threats to circumvent the Senate with recess appointments.

Sen. Susan Collins, R-Maine, who was outspoken Wednesday about her shock at Gaetz’s appointment and her alarm at the possibility that Trump would go around the Senate to install him, adopted a more conciliatory tone by Thursday.

“There may be cases where the Democrats have proposed unreasonable roadblocks and are slow-walking nominees that are not controversial,” she told reporters. “In those cases, maybe you can make a justification for having recess appointments.”

But others warned that the responsibility for ensuring that confirmations proceed smoothly lay with Trump, not the Senate.

“If we get good candidates we will be able to move through the nominations process hopefully really readily and that’ll be good for the president,” said Sen. Lisa Murkowski, R-Alaska. “But when you put forward picks that are really going to generate controversy, and not just controversy on one side of the aisle, it is going to take longer.”

Senators seemed generally unprepared, however, for dealing with what might be a nuclear option for Trump: forcing the Senate to recess so that he can name unpopular nominees without getting them confirmed. Though the Constitution dictates that the Senate can offer advice and consent on nominees, it also gives the president authority to adjourn Congress if there is a disagreement between the two chambers about whether to adjourn.

Some professed ignorance about that part of Article II when asked whether they feared that Trump might exploit it.

“I don’t think he can do that,” Sen. Mike Rounds, R-S.D., told reporters. “I have not heard that theory.”