Republican senators are growing increasingly frustrated with the White House for foisting upon them a parade of controversial cabinet nominees whom they believe haven’t gone through a proper vetting process.

Throughout much of the Trump presidency, those frustrations have been shielded from public view out of deference to the president’s right to pick his own team. But a revolving door of high-level staff departures has forced GOP leaders to set aside valuable floor time—and expend already thin political capital—on tricky confirmation fights over controversial replacements. And not everyone is pleased.

“I understand that the president wants his people—and we want to be deferential as much as we can—but it would be nice to know some of the issues that come up after the fact, before the fact,” said Sen. John Thune (R-SD), the third-ranking Republican in the Senate.

The latest, most glaring pressure point—and the one to which Thune was alluding—emerged this week with the nomination of Rear Adm. Ronny Jackson to lead the Department of Veterans Affairs. Jackson, who currently serves as the top White House physician, has been accused of being drunk on the job, over-prescribing medications, and creating a hostile work environment.

He has either denied, or stressed his desire to explain away, those allegations. But an equally significant concern among Republican senators is that those allegations surfaced not from an internal White House review, but through a vetting process conducted by the Senate Committee on Veterans’ Affairs, which is overseeing the confirmation.

“In this case, I get the sense that there wasn’t any vetting, so I think that calls [the White House’s vetting process] into question,” Sen. Shelley Moore Capito (R-WV) told The Daily Beast.

Jackson’s confirmation hearing, which was initially scheduled for Wednesday, has been put on hold as the White House digs in to defend him. But with little overt support coming from Republican lawmakers, that defense might prove both brief and useless. On Wednesday night, The Washington Post reported that Jackson was considering dropping his bid.

Should he withdraw, it would save lawmakers a potentially difficult vote. But it would do little to ease the tensions that have emerged between Congress and the administration. In addition to Jackson, the Senate is also considering nominees for the State Department and the CIA, alongside various ambassadorships.

They also are being forced to grapple with the ethical lapses of cabinet members they’ve already voted to confirm, chief among them Environmental Protection Agency chief Scott Pruitt, whose own waves of controversy—from his living arrangements to his travel expenses—have sparked additional criticism of the White House.

“If they prove to be true,” Sen. Susan Collins (R-ME) said of the allegations against Jackson, “it does raise questions about the vetting process, as do the allegations involving the allegations against Scott Pruitt that date back to his days in Oklahoma.”

Many Republican senators remained reticent to publicly criticize the administration’s vetting of high-level nominees. But aides lamented what they viewed as a haphazard process that appeared more focused on whether a prospective nominee disqualified himself or herself by saying something negative about the president than whether he or she was qualified for the post.

“The deliberation before nominating Ronny Jackson appears to have been little more than something like, ‘Ronny told a funny joke during my physical. Let’s make him VA secretary,’” a senior Republican aide told The Daily Beast. “Perhaps the staff dedicated to combing potential staff assistants’ Twitter feeds for phrases like ‘Cheeto Jesus’ and ‘tiny hands’ should be involved in the vetting process of senior staff and cabinet nominees.”

Jackson’s nomination has been, for many on Capitol Hill, the perfect illustration of this problematic vetting process. His primary qualification for the post seemed to be his proximity to Trump and his praise of the president’s health when explaining the results of a physical on live television. Indeed, even before the allegations against him came to light, lawmakers were concerned that Jackson did not have the leadership experience necessary to run a behemoth of a department that has vexed top military leaders, seasoned bureaucrats, and high-profile business executives before.

“Particularly with a position this important, this big, it’s concerning that they didn’t have a better vetting process. I had my concerns from the beginning in terms of qualifications and experience, but these new allegations are something that should have been explored and explained before he was offered up,” Sen. Jeff Flake (R-AZ) said in an interview. “This is not ideal. In particular when it’s someone so close to the president, but without any general qualifications for the job. That’s a concern that’s shared by a lot of my colleagues.”