As President-elect Donald Trump is seeing a rising wave of his brand of America First populism, he has noted some Republicans are some of his most loathed political rivals.
Including the three remaining moderate senators who voted to impeach Trump after he left office, there are nine Republican senators who could prove to make passing Trump's most controversial Cabinet nominees difficult — if not derail altogether his legislative agenda in the Senate.
The GOP is expected to hold a narrow 53-47 Senate majority with the Sen.-elect David McCormick, R-Pa., victory headed for a recount against Sen. Bob Casey, D-Pa., so the margins are slim.
The Senate holds the advise-and-consent role over Trump's Cabinet nominees and the self-proclaimed "firebrand" former Rep. Matt Gaetz, R-Fla., has his own detractors, giving him a large mountain to climb to garner enough support to be confirmed to replace Attorney General Merrick Garland.
In addition to Gaetz, the nominations of Robert F. Kennedy Jr. as Health and Human Services secretary and Pete Hegseth as defense secretary figure to face GOP skepticism from Trump's denounced Senate "RINOs" (Republicans in name only).
Trump can only stand to lose three, since a 50-50 Senate tie would give Vice President-elect JD Vance the deciding vote in the upper chamber.
Nine potential Senate GOP antagonists for Trump's nominees:
Sen. Susan Collins, R-Maine
The only Republican senator up for reelection in 2026 in a state that Vice President Kamala Harris won will be targeted by the left to flip a seat, and Trump has his own ax to grind here.
Collins had been one of Trump's biggest skeptics — she voted to impeach Trump after he left office in 2021 — and she also was shocked by the announcement of Trump's intention to nominate Gaetz as attorney general.
"Obviously, the president has the right to nominate whomever he wishes," Collins said. "But this is why the Senate's advise and consent process is so important. I'm sure that there will be many, many questions raised at Mr. Gaetz's hearing, if in fact the nomination goes forward."
Collins has also expressed skepticism over Kennedy as HHS secretary, according to The Hill.
Sen. Lisa Murkowski, R-Alaska
After she voted to impeach him, Trump had backed primary challenges against Murkowski — and denounced her support for ranked-choice voting and now-defeated Rep. Mary Peltola, D-Alaska, against Republicans in the past.
Murkowski rejected Gaetz's nomination as not "serious."
"I don't think it's a serious nomination for the attorney general," Murkowski said. "I'm looking forward to the opportunity to consider somebody that is serious. This one was not on my bingo card."
In kind, Trump backers have denounced GOP skeptics as "not serious" lawmakers, considering they had voted to confirm many of President Joe Biden's shaky nominees.
Murkowski is also tepid over Hegseth for defense.
"Wow," she told The Hill. "I'm just surprised. I'm not going to comment on whether it's good, bad or indifferent, I'm just surprised, because the names that I've heard for secretary of defense have not included him."
Sen. Bill Cassidy, R-La.
One of the seven who voted to impeach Trump after he left office in 2021 — and one of just three remaining in the Senate with those two above — Cassidy dodged a question last week on Gaetz by claiming he has to fix a toilet.
"I'm trying to go fix a toilet between getting back for a vote," he said, Politico reported. "Life's a little hectic right now."
Sen. Mitch McConnell, R-Ky.
McConnell is no longer the incoming Senate majority leader for his break from Trump after Jan. 6.
There could be retaliatory actions against Trump's nominees or agenda.
"Looking at his track record, he's never cowed to Trump on things, especially as they relate to the Senate and the Senate's role," a Senate GOP aide told The Hill.
Sen. Todd Young, R-Ind.
Young is a former McConnell acolyte and could remain one after refusing to endorse Trump for president.
The former chair of the Republican Senatorial Committee under McConnell was asked for comment about Gaetz's nomination last week but reportedly pivoted by praising Sen. Marco Rubio, R-Fla., on being nominated to be the next secretary of state, a show of potential opposition, according to Politico Playbook.
Sen. Thom Tillis, R-N.C.
Another 2026 reelection campaign target for Democrats in a key battleground state, if he decides to run. Trump won by 3.5 percentage points over Harris, but Democrats have used the state to chip away to GOP support in the Sun Belt.
Tillis has already noted that Gaetz will not have the votes to be confirmed as attorney general.
"I have very few skills, vote counting is one, and I think he's got a lot of work to get 50," Tillis said without elaborating on how he might see his vote.
Sen. John Cornyn, R-Texas
While Cornyn is GOP senator in a red state, he could be a target for a Republican primary, particularly if he lives up to his vow to be free of supporting Republican agenda items he deems out of bounds, saying he and McConnell are "liberated" after being rejected for Senate GOP leadership positions.
Cornyn, who has been criticized heavily by Newsmax host Chris Salcedo, did not say if he opposed Gaetz's nomination, but said he "absolutely" wants to review an unreleased congressional ethics report on Gaetz.
Cornyn told reporters "there should not be any limitation" on the Senate's investigation as lawmakers consider whether they should confirm Gaetz to head the Justice Department, "including whatever the House Ethics Committee has generated."
Asked if that means he wants to see the ethics report, he replied: "Absolutely."
Sen.-elect John Curtis, R-Utah
Joining the Senate from the House, where he served since 2018, Curtis replaces anti-Trump Sen. Mitt Romney, R-Utah, one of the GOP senators ostensibly forcing himself out of a reelection campaign after voting to impeach Trump after he left office.
Reports have Curtis as a centrist cut from the same cloth as Romney, heading the House Conservative Climate Caucus and opposing climate skepticism.
While Curtis did not vote to impeach Trump, he had supported censuring him after Jan. 6.
Gaetz campaigned for Curtis' primary opponent in March, making support for Gaetz unlikely, even if opposing Trump might not be obvious.
Curtis has come out against Trump's desire for recess appointments, too.
"Sen.-elect Curtis believes that every president is afforded a degree of deference to select his team and make nominations," Curtis chief of staff Corey Norman told local Salt Lake City TV last week. "He also firmly believes in and is committed to the Senate's critical role to confirm or reject nominations based on information and insight from confirmation hearings."
Sen. Joni Ernst, R-Iowa
Ernst endorsed Trump for president and is not regarded as a "RINO," making her the least likely opposition on this list, but she was jilted in a bid for a GOP leadership position so she might be less inclined to toe the Senate GOP line.
Ernst has taken a cautious approach on commenting on Gaetz or the director of national intelligence-nominee, Tulsi Gabbard, according to The Hill.
"I've had a relationship with her," she told the outlet. "It might be a little unconventional, but at the same time, she might bring value to us too. So we'll have to sort through all that."
Among the topics of concern for Ernst, a 23-year military veteran and member of the Senate Armed Forces Committee, is Gabbard's past statements on dictators Vladimir Putin of Russia and Bashar al-Assad of Syria.
"We'll have to talk about that," Ernst told The Hill.
Ernst is also up for reelection in 2026, making her a potential target for Democrats in a state former President Barack Obama won in 2008 and 2012 before Trump flipped it back red.