Americans vote on Tuesday in midterm elections that will decide control of the House of Representatives and the Senate. But the results will have wider implications. For President Donald Trump, the vote is a referendum on his second term. For both parties, and for the contenders hoping to succeed him, it will shape the race for the 2028 presidential nomination and the direction each takes after Trump. Here is what is at stake for the key players:

Donald Trump

Most indicators suggest that an electoral setback is likely for the 80-year-old commander-in-chief. An unpopular war with Iran, high energy prices and a sustained affordability problem have turned voters against Trump and his party ahead of Tuesday’s election. Trump’s approval rating, an average of around 37%, is among the lowest in recent memory for a President leading his party into a major election.

Trump has to defy the odds and political gravity to hold on to both the House of Representatives and the Senate. But if he does, his position as one of the most consequential and powerful American politicians of the last 50 years will be greatly strengthened. Control of both chambers would shield his signature policies, including global tariffs and the war on Iran, from congressional challenges over funding and oversight.

Presidents in the last year or two of their terms are often referred to as “lame ducks”, capable of doing little of consequence while the country looks beyond them towards their successor. But a victory will strengthen Trump and his hand in shaping the Republican Party’s 2028 presidential nomination.

Losing both the House and the Senate to the Democrats would mean a bruising defeat for the President. The House has the power to approve government spending and launch investigations into the administration. The Senate confirms the President’s nominees, including judges and cabinet officials, holds key powers on foreign policy matters, and must also approve spending bills once they pass the House.

This would give the Democrats substantial power to frustrate Trump’s domestic agenda and embarrass his administration with corruption investigations. Even a split result, with Democrats winning only the House, would hand them subpoena power and leverage over spending, though a Republican Senate would continue to approve Trump’s nominees.

Republicans

For much of the last few years, the party has been reduced to an instrument of Trump’s will. Few modern Presidents have dominated their parties as Trump has. That dominance will be tested on Tuesday.

A poll by Politico found that Trump’s hardline Make America Great Again (MAGA) voters will likely back him even if he loses the midterms. In fact, 54% of respondents said the loss of both the House and the Senate would be a sign that the party needed to hew closer to Trump’s policies. Trump voters who do not identify as MAGA disagree. Some 44% of such respondents said the loss of both chambers would be a sign that the party must distance itself from the President.

More moderate voters have expressed less support for the President’s hardline views on immigration. A decisive Republican defeat could spark a battle within the party for the future of the party.

The Democratic Party

The party suffered a major setback in 2024, when it lost the White House and the Senate to Republicans while also failing in its attempt to take back the House of Representatives. The Democrats have been on a quest to redeem themselves for the last two years, while fighting off concerns that the party is too weak, out-of-touch and disorganised to beat Trump. Winning one or both chambers will do much to restore the party’s confidence ahead of the 2028 presidential election. A bad result will only further spotlight its weaknesses.

The party’s moderate establishment is at odds with a new generation of progressive, Left-wing politicians such as New York City Mayor Zohran Mamdani. On Sunday, Haley Stevens, a Democrat, broke with her party to endorse the Republican candidate for US Senate in Michigan. Stevens narrowly lost her bid to become the Democratic candidate for the seat to progressive, Left-wing candidate Abdul El-Sayed.

The defection sent alarm bells ringing within the party as the Democrats have to retain this seat if they have any hope of taking control of the Senate. More broadly, it reinforced the damaging perception that the party is too divided to get its house in order, even for must-win elections.

The 2028 presidential election battle will also begin in earnest within months of midterm elections. Primary fights are divisive affairs even in the best of times. If the Democratic Party cannot handle its divisions to win even a Senate seat in Michigan, it will raise questions about how it will fare when its top leaders jostle for the party’s presidential nomination.

Republican 2028 hopefuls

Three Republican names stand out as potential candidates for the 2028 election: Vice President JD Vance, Texas Senator Ted Cruz and Secretary of State Marco Rubio. Rubio has expressed a lack of interest in running and said he will support Vance’s candidacy. The fortunes of the other two will be affected by Tuesday’s results.

Vance is the frontrunner and the politician most closely tied to Trump. A victory on Tuesday will likely lead him to move closer to Trump’s policies to win support from the party’s base. A Republican defeat might signal that the country is tiring of Trump and his policies. This poses a problem for Vance, who will have to balance loyalty to the president with distancing himself enough to avoid being tainted by Trump’s unpopularity, a difficult balance that Kamala Harris tried and failed to strike in the 2024 election.

Cruz has been careful to carve out an independent position from the White House on key issues, including by speaking out against an increasingly troubling acceptance of racism and white supremacist influencers within the Republican Party. A bad result in the midterms could bolster Cruz’s call for the party to return to its more traditionally conservative roots. Cruz remains a divisive figure even within his own party and likely lacks the backing to challenge Trump’s hold over the Republican base.

Democratic hopefuls

A long list of Democratic politicians are eyeing nomination for the presidency. Former Vice President Kamala Harris, California Governor Gavin Newsom and Representative Alexandria Ocasio-Cortez are some of the key names in the mix.

If Trump and the Republican Party face severe setbacks in Tuesday’s election, it could spark an intense competition within the party. Whoever wins the Democratic Party’s nomination could enter the race with an advantage, facing a Republican nominee saddled with an unpopular outgoing president, an unpopular war with Iran, and high prices. Managing the party’s internal divisions and personal rivalries over the coming months could become crucial.