Congress begins a new session today. Here are five things you should watch

As the world approaches the new year, lawmakers gather at the US Capitol to usher in a new Congress.

Friday marks the start of the 119th Congress with Republican majorities in both the House and Senate.

That marks a Republican trifecta, given that President-elect Donald Trump is also returning to the White House later this month. The US has not seen unified control of the three branches of government since 2017, when Trump was last in office.

Republicans are eager to get started on an ambitious to-do list, but things may not be easy — and their majorities in both houses of Congress leave little room for dissent. The first test of the party's unity comes Friday with the House leadership election.

Here are five things worth watching as the new session of Congress begins:

Republicans may have a majority in the House, but not by much.

And will be put to the test immediately after the session begins. The House cannot certify election results or pass laws until lawmakers choose their next speaker, the House Leader.

Despite Trump's endorsement, incumbent Speaker Mike Johnson faces opposition from several members in his caucus who remain unconvinced he deserves a second chance.

The party's majority is so slim that if Johnson loses just two Republicans in his campaign, it could lead to a series of votes until Republicans rally around a lawmaker. In 2023 it took 15 rounds of voting and four days for Kevin McCarthy to win the presidency.

Johnson already faces a firm no from Rep. Thomas Massey of Kentucky, but several other Republicans have placed themselves in the undecided column.

The GOP remained with a five-seat majority when the final House races were called in the 2024 election. But that shrunk after Trump selected several members of the House of Representatives to serve in his administration.

“Do the math,” Johnson said during a news conference in early December. “We have nothing to spare.”

In the Senate, lawmakers have already chosen their majority leader: South Dakota Sen. John Thune won the internal GOP vote.

That means the Senators can get down to business on Friday, but they will face challenges in other ways. Lawmakers are expected to begin a series of confirmation hearings on some of Trump's controversial issues appointed to the cabinet.

The Senate must sign off on about 1,200 appointments for the new president's administration, but some will come with tense hearings that draw public attention. They will first appear before a Senate committee and answer questions before the full chamber votes.

The nominations include Trump's pick for secretary of defense, Pete Hegsethwho has been facing sexual assault allegations since 2017, which he denies, as well as his pick for Secretary of Health and Human Services, Robert Kennedy Jrwho is a vaccine skeptic with a history of spreading misinformation.

Trump's picks were spotted touring Capitol Hill last month to win over Republican senators. But the nominees will have to appear before bipartisan committees — meaning the hearings could get heated as senators from both parties use their platform to address criticisms and grievances.

However, the Senate may choose to expedite confirmation hearings from some national security nominees — after a New Year's Eve terrorist attack in New Orleans that left 14 dead and a vehicle explosion outside Trump's Las Vegas hotel.

“The US Senate must confirm President Trump's national security team as soon as possible. Lives depend on it,” Wyoming Sen. John Barrasso wrote in an X post.

A nomination that clears a committee typically faces no opposition across the Senate, but given some of the initial backlash over Trump's selection, the road to confirmation could be bumpy.

One item rising to the top of the legislative to-do list for Congress is addressing the Trump Tax Cuts and Jobs Act of 2017, which expires in 2025.

The 2017 legislation – which was passed at a time when Republicans controlled both the House and Senate – included a $1.5 trillion (£1.2 trillion) overhaul of the tax code, changes to tax brackets and reduced tax rates for most taxpayers.

It marks the biggest tax overhaul in decades. The biggest cuts targeted businesses and the wealthy, which Democrats called for repeal.

Trump campaigned on the economy, promising to expand tax cuts, further cut corporate taxes and eliminate taxes on tips, overtime pay and Social Security income.

How Congress will do it — an extension of the 2017 bill, a mix of old and new legislation, or by other means — is up in the air.

Preserving provisions from the 2017 tax cuts. will add about $4 trillion to the deficit over the next decade, according to the Congressional Budget Office. That may not sit well with many hard-line Republicans, who are staunchly opposed to increasing the nation's debt.

Expect to see legislative changes on several key Republican priorities, ranging from curbing illegal immigration to reducing government regulations.

There may be proposals to cut military aid to Ukraine, impose new tariffs, reduce clean energy costs and improve border security.

At a press conference in November, Johnson outlined a Republican agenda that aims to reduce inflation, secure the border, restore the country's energy dominance, implement “educational freedom” and “drain the swamp.”

Lawmakers will also have to consider the debt ceiling — the total amount the U.S. can borrow to meet its obligations. The issue already arose in late 2024 when lawmakers faced a government shutdown.

Trump has urged lawmakers to raise or even freeze the debt limit in any spending deal, but the provision was removed from the final version of the bill passed by both chambers.

It is possible for several priorities to be combined into what is known as a reconciliation bill, which allows Congress to pass a tax, spending and debt limit bill with only a majority vote. This method avoids the possibility of a filibuster in the Senate, where opposing lawmakers could delay or even defeat a vote.

However they decide to approach it, lawmakers may be spending more time on Capitol Hill tackling their priorities next session.

New Senate Majority Leader John Thune has scheduled significantly more days and weeks for the Senate — including business days on Mondays and Fridays, traditionally considered travel days.

The end of the last congress offered a glimpse of influence on Trump and his allies are on the agenda of Congress.

Tech billionaire Elon Musk, who is tasked with advising the Trump administration on government spending cuts, has posted dozens of times on his social media platform X to condemn the spending deal Johnson spearheaded with Democrats to avert a government shutdown .

Trump and Vice President-elect J.D. Vance joined in, and the bill was crushed.

Both Trump and Musk have threatened to withhold funding and endorsements from Republican incumbents who supported the bipartisan spending bill, raising questions about how much influence they will have on the legislative agenda.

Musk and pharmaceutical entrepreneur Vivek Ramaswamy may have more opportunities to weigh in. The two will jointly lead a newly formed advisory committee focused on cutting regulations and spending.

Across the aisle, Democrats are regrouping with hopes of winning back the House in the 2026 midterm elections. Expect to see left-of-center lawmakers jockeying for influence.

All caucuses in the party hope to shape its future — like the Problem Solvers Caucus, a group of lawmakers focused on advancing bipartisan legislation; The Blue Dog Coalition, a group of centrist Democrats; and the center-left, “pragmatic” New Democratic Coalition.