WASHINGTON  —  Since he began taking over the Republican Party nearly a decade ago, President-elect Donald Trump has demanded increasing levels of loyalty from lawmakers who serve in Congress.

With few exceptions, they have gone along, refusing to convict him in two impeachment trials and, even after he was convicted of 34 felonies, helping him win a second term in the White House as he plowed through a Republican primary and general election after falsely denying his 2020 loss.

Now, members of the Senate will face another test: Whether to cede their long-held independent authority under the Constitution to review an increasingly controversial group of Cabinet picks.

Many senators in both parties have already expressed concerns about some of Trump’s selections, but Trump has said he expects the body to test a controversial tactic that would let him bypass the confirmation process.

In the last several days, Trump has nominated Pete Hegseth, a Fox television host and veteran who has never held a leadership post, as his secretary of Defense; Tulsi Gabbard, a former Democratic House member accused of spreading Kremlin talking points, as his director of National Intelligence; and Matt Gaetz, a Florida Republican who resigned his seat in the House on Wednesday while facing a congressional investigation into sex trafficking, as his attorney general.

Then on Thursday, Trump named Robert F. Kennedy Jr., a vociferous vaccine skeptic who has promoted false conspiracy theories concerning healthcare, to lead the Department of Health and Human Services.

Trump is known for defying tradition and going against the grain, but the recent appointments suggest a larger agenda, some political observers say.

“There is a difference between having a broader ideological mix and choosing a [accused] sex trafficker for attorney general of the United States,” said Marc Short, who served as Trump’s legislative affairs director during his first term and as chief of staff to former Vice President Mike Pence.

“I think he’s trying to disrupt,” Short said of Trump. But “I’m not convinced that it’s clearly thought through.”

Former House Speaker Kevin McCarthy, the Bakersfield Republican whose career in Congress was upended when Gaetz led a rebellion against him, predicted that at least the Gaetz nomination would fail, telling Bloomberg Television on Thursday that he “won’t get confirmed, everybody knows that.”

McCarthy called the nomination “a good deflection,” hinting at a popular Washington theory that Gaetz, even if defeated, could help Trump win approval of other controversial nominees by using up whatever willpower Republican senators have to take on the new president next year.

At the center of it all is Sen. John Thune, a South Dakota Republican who won an internal vote to become Senate majority leader on Wednesday. He replaces Kentucky Sen. Mitch McConnell, who occasionally clashed with Trump during his first term but prevented an all-out intraparty war by largely acquiescing to the president. The Senate under Thune will be even more Trump-friendly, with more members who come into office with Trump’s support, while some of the more skeptical Republicans are no longer in office.

Trump had mixed results with his first-term nominations, even as he chose from an inexperienced talent pool. Several of his high-level nominees faced drawn-out battles — a few withdrew, but most were eventually approved.

Before Thune defeated two of his colleagues to win the leadership post, Trump said on social media that he wanted the new Senate leaders to push his nominees through using recess appointments, where the Senate would declare itself closed for business for 10 days so the president can appoint a Cabinet secretary for the remainder of the two-year session.

The tactic, conceived in the horse-and-buggy days when Congress met part time, would probably be challenged in court. Opponents argue against their routine use, and members of the Senate are historically protective of their role as a check on the executive branch.

Thune told South Dakota reporters Wednesday that he would prefer to avoid a recess appointment but did not rule it out.

“I’m willing to grind through it and do it the old-fashioned way,” he said, according to the Sioux Falls Argus Leader.

He reiterated that point to ABC News on Thursday, promising “we expect our committees to do their jobs and provide the advice and consent that is required under the Constitution.”

Lawmakers in both parties have already said they want to know more about the House Ethics probe into Gaetz, which was closed when he resigned his seat. The comments signal that they do not want to cede their right to review his record. One lawmaker who said he “absolutely” wants to see the House report was Sen. John Cornyn of Texas, a high-ranking Republican member of the Judiciary Committee who ran against Thune for majority leader.

The use of recess appointments to avoid the Senate is a concern to some who’ve worked in the federal government.

Richard Painter, former chief White House ethics lawyer under President George W. Bush, said that immediately adjourning the Senate at the new president’s direction would signal a dark day for the country.

“This is the way it works in dictatorships,” said Painter, who ran for Senate in Minnesota in 2018 as a Democrat. “To have a president sworn in and then immediately dissolve Congress? Absolutely nuts.”

But the pressure to push Trump’s preferred choices is mounting. Sen. Tommy Tuberville of Alabama, one of Trump’s most ardent allies, warned would-be dissenters during an appearance on Fox Business that if they stand in the way of Trump’s agenda, “we’re gonna try to get you out of the Senate.”

The Senate has a long tradition of protecting its status, as one of two houses in Congress, as part of a co-equal branch of government, even if the president is in the same party. The late Majority Leader Harry Reid of Nevada rankled some fellow Democrats in 2009 when he said in an interview: “I do not work for Barack Obama. I work with him.”

But a former Reid adviser, James Manley, said he believes Trump is consciously trying to erode that boundary, and he’s skeptical that Republican lawmakers have the stomach to stand up to him.

“The House is broken. They’ll do whatever he wants,” Manley said. “Now, he’s turned his attention to the Senate.”

Ben Olinsky, senior vice president of structural reform and governance at the liberal Center for American Progress, said that how the Senate handles this moment — where Trump is simultaneously putting forward deeply questionable candidates and demanding the Senate allow them to sail through without vetting — “will tell us a lot about what’s going to happen in the next couple of years.”

“I absolutely think it’s a test of independence and also integrity for them,” Olinsky said. “It may be a direct loyalty test from the president.”