When Donald Trump returns to the Oval Office in January, he will preside over a coveted “unified government”, with his party controlling the White House, the Senate and the House of Representatives.
But a handful of more moderate Republican senators could still stymie the president-elect’s legislative agenda, and even block the confirmation of some of his most controversial cabinet nominees.
Republicans have a slim majority in the Senate, with 53 seats compared to the Democrats 47. The Republicans have 220 in the House, while the Democrats are expected to have 215. But that lead could shrink when Trump appointees such as Elise Stefanik and Mike Waltz resign to take up their new posts.
“These are still pretty close margins on the Hill. There are institutional guardrails there that are going to come into play,” said Kevin Madden, a senior partner at Penta, an advisory group, and a veteran of Republican presidential campaigns and Capitol Hill.
Those guardrails were on display last week, when controversial former congressman Matt Gaetz withdrew his nomination for US attorney-general after closed-door meetings with senators.
Four key Republican figures were among those who reportedly took issue with Gaetz’s appointment: outgoing Senate majority leader Mitch McConnell; Susan Collins of Maine, Alaska’s Lisa Murkowski, and incoming Utah senator John Curtis.
The party’s slim majority means all eyes will be on the four, along with a handful of other senators, as the administration gears up for a gruelling confirmation process for some other controversial nominees and legislative battles over everything from funding the government to plans for sweeping tax cuts.
Many Washington veterans say the relatively small group of Republican lawmakers could torpedo several of Trump’s other cabinet picks.
“It was not just one brush fire,” Madden said, referring to Gaetz, who has faced swirling allegations of sexual misconduct, including having sex with underage girls, but denies all wrongdoing. “There were four or five [fires] set simultaneously,” he added, pointing to other nominations who have raised alarm bells in Washington.
Critics have questioned whether three picks in particular will stand up to Senate scrutiny. Tulsi Gabbard, nominated for director of national intelligence, Pete Hegseth for defence secretary and Robert F Kennedy Jr for health and human services secretary.
Gabbard, a National Guard veteran, has expressed pro-Russian views and has been criticised for praising Syrian leader Bashar al-Assad, while Hegseth has faced questions about an allegation of sexual assault. Hegseth was never charged with a crime and denies all wrongdoing but has agreed a confidential financial settlement with his accuser.
Kennedy, meanwhile, has critics from the right, who dislike his previous comments in favour of abortion rights, and the centre, who are concerned about his vaccine scepticism.
At an event in Washington last week, Collins said Kennedy and other health appointees — including celebrity doctor Mehmet Oz to run the Centers for Medicare and Medicaid Services — should face “extensive committee investigations” before any votes are held.
The moderate senator, who has represented Maine for almost three decades, has occasionally opposed Trump.
In the president-elect’s first term, she was one of seven Republicans who voted against his efforts to overturn the Affordable Care Act, more commonly known as Obamacare. Three years later, she was the only Republican senator to vote against Trump’s eleventh-hour nomination of conservative justice Amy Coney Barrett to the US Supreme Court.
But Collins has also acted in lockstep with her party more times than not, including voting to confirm Brett Kavanaugh as a Supreme Court justice.
Murkowski, a fellow moderate and long-serving senator from Alaska, has a similarly independent streak. In 2010, she lost a Republican primary to a right-wing Tea Party candidate, but won re-election as a write-in — a candidate whose name is written in by voters, even though they are not on the ballot. In the first Trump administration, she opposed Kavanaugh’s nomination.
Curtis is less of a known quantity. An outgoing Republican congressman, he was elected to the Senate this month to replace Mitt Romney, an outspoken Trump critic who decided not to seek re-election.
While Curtis has been less publicly critical of the president-elect than Romney, he is seen as a moderate and has embraced liberal causes such as combating climate change and protecting same-sex marriage. He also declined to endorse Trump in the 2024 primaries.
Meanwhile, many on Capitol Hill expect McConnell will not shy away from confronting Trump in the new congress. The Kentucky senator is handing over Senate leadership to John Thune in January after nearly two decades as the chamber’s top Republican, liberating him from re-election worries.
McConnell has a complicated relationship with the president-elect. He refused to support Trump’s efforts to overturn Biden’s victory in 2020 and blamed him for inciting the January 6 2021 Capitol riots. But he ultimately endorsed the former president’s second bid for the White House — and was mocked by Trump for doing so.
He has made no secret of their long-running disagreements, including over matters of foreign policy — McConnell is seen as a Russia hawk and staunch supporter of Nato — and the institutional norms of the Senate.
Other names floated as possible roadblocks to Trump include Bill Cassidy, the Louisiana senator who, along with Collins and Murkowski, was one of seven Republicans who voted to convict Trump of inciting an insurrection in his second impeachment trial; and Indiana Republican Todd Young, who refused to endorse Trump’s latest White House run.
Several Senate appointments to come could also tip the balance on Trump’s agenda.
Moderate Ohio governor Mike DeWine has yet to appoint someone to replace JD Vance — who will resign his Senate post to become vice-president — while Florida governor and Trump’s former primary rival Ron DeSantis has to choose who should replace outgoing senator Marco Rubio, Trump’s pick for secretary of state. One candidate for the role is the president-elect’s daughter-in-law, Lara Trump but DeSantis could pick a figure seen as less beholden to the Maga movement.
Still, many hardened Washington veterans, including most Democrats, believe few Republicans will be ready to fight Trump given his tight grip on the party and tendency to seek revenge on his critics.
“We saw tentative attempts to grow a spine when at least a handful of Republicans refused to even entertain the idea of confirming Gaetz . . . but I am not so sure how many other times that is going to happen,” said Jim Manley, a former aide to Democratic Senate leaders including the late Harry Reid and Ted Kennedy.
He added: “I am just not convinced that when push comes to shove, and the president is putting it all on the line, enough Senate Republicans will stand up to him.”