President Trump speaks to members of the media last month. He is accompanied by Senate Majority Leader Mitch McConnell (R-Ky.), left, and Sen. Roy Blunt (R-Mo.). (Susan Walsh/AP)

The Republican Party has spent most of the past three years kowtowing to President Trump, terrified of inflaming the conservative base he has cultivated. But there are signs that GOP senators are now more willing to stand up to the Trump White House, even publicly.

The rebukes are generally on legislative issues and have little to do with Trump’s conduct, and they are hardly a sign of a large-scale revolt within GOP ranks. At the same time, they do suggest the relationship between Trump and the legislative branch is deteriorating.

The latest source of discord is over Trump’s apparent desire to clean house on top administration officials in charge of immigration-related issues. A surge of illegal border crossings and asylum seekers has already spelled the end for Homeland Security Secretary Kirstjen Nielsen. Senate Finance Committee Chairman Charles E. Grassley (R-Iowa) this week warned Trump against putting anybody else on the chopping block, especially Lee Francis Cissna, the director of U.S. Citizenship and Immigration Services.

"The president has to have some stability and particularly with the number one issue that he’s made for his campaign, throughout his 2½ years of presidency,” Grassley said. “He’s pulling the rug out from the very people that are trying to help him accomplish his goal.” (Grassley, a proponent of wind energy, has also called Trump’s recent comments suggesting wind farms cause cancer “idiotic.”)

Other senators have also expressed concern about how the dismissals have been handled. On Tuesday, Sen. John Neely Kennedy (R-La.) suggested the White House’s tendency to bash outgoing figures like Nielsen would make it difficult to find qualified replacements.

“Would one of you guys take a job there?” Kennedy asked reporters, according to Igor Bobic of HuffPost. When the questions was turned back on Kennedy, he said, “As much as I respect the president, not if I’m going to have his staff members when I decide to leave cut me to pieces anonymously.”

Senate Appropriations Committee Chairman Richard C. Shelby (R-Ala.) was also quoted this week apparently expressing exasperation with acting White House chief of staff Mick Mulvaney. As the New York Times reported:

Mr. Shelby told Senator Patrick J. Leahy of Vermont, the committee’s top Democrat, that Mr. Mulvaney was “the most dangerous man” in Washington, according to three people familiar with the exchange.

Mr. Shelby has not repeated that in public, but when a reporter on Capitol Hill asked him about Mr. Mulvaney last week, the senator tartly interrupted to offer a correction.

“You mean the acting chief of staff?” he said before walking away.

Trump’s new nominees for the Federal Reserve have also stirred dissension — especially former GOP presidential candidate Herman Cain, who exited the 2012 race amid sexual harassment accusations. CNN reported that Senate Majority Leader Mitch McConnell (R-Ky.) has told Republicans senators to express their concerns directly to the White House. Former majority whip Sen. John Cornyn (R-Tex.) publicly urged Trump to consult the Senate before making such nominations, “rather than have the embarrassment for the nominees or for the President or for senators.” And Sens. Cory Gardner (R-Colo.) and Mitt Romney (R-Utah) have already come out against Cain.

McConnell has also in recent weeks declined Trump’s entreaties to try to pass a new health-care bill, forcing Trump to back off the issue for now. And the Senate last month voted to stop Trump from declaring a national emergency on the Southern border and voted to end U.S. involvement in the war in Yemen as a punishment for Saudi Arabia’s killing of Washington Post columnist Jamal Khashoggi. Trump simply vetoed the former, but those two votes represent perhaps the Senate GOP’s biggest legislative rebukes of Trump yet.

The national emergency situation is an important caveat to all of this. While Republican senators rather publicly cautioned Trump against making the move in the first place — in large part because they worried about a Democratic president taking advantage of the new precedent — they tempered their criticism once Trump actually went through with it. Some of them ultimately voted to stop it, but their criticism was watered down, and some who publicly suggested Trump not do it fell in line.

It’s notable, though, that there appears to be an increasing willingness to speak up. Perhaps that’s in part because a newly divided Congress is unlikely to pass significant legislation with the 2020 election looming. Perhaps it’s because these GOP senators truly worry about good people inhabiting Trump’s administration, after Trump’s unwieldy governing style forced out Defense Secretary Jim Mattis. Or perhaps they’ve figured out ways to somewhat subtly make clear they’re not thrilled with what’s happening at 1600 Pennsylvania Avenue, after years of being deathly afraid of being turned into the next Bob Corker, John McCain or Jeff Flake.

Whatever the case, it’s worth staying tuned.