The US midterm elections, held every two years, take place halfway through a president's four-year term. Voters elect members of Congress, the federal legislative branch responsible for creating and passing national laws, making the elections a measure of public opinion on the president's performance.
The results determine "which political party... controls Congress and how easy it is for the president to carry out his plans".
With Republicans holding narrow majorities in both chambers of Congress, the elections will determine whether President Donald Trump retains legislative support for the remainder of his term or faces greater opposition to his agenda, says the BBC.
Who is being elected?
All 435 seats in the House of Representatives, the lower chamber of Congress, are up for election. Members serve two-year terms, and the chamber is "commonly where proposed laws are introduced and debated".
In the Senate, the upper chamber, 35 of the 100 seats are being contested. Senators serve six-year terms and, among their primary duties, "approve or block proposed laws that have been received from the House".
Voters will also elect state-level politicians, with gubernatorial races in California, Florida, Georgia and Michigan attracting significant attention.
What is the current balance of power in Congress?
Republicans currently hold narrow majorities in both chambers.
In the House of Representatives, Republicans have 218 seats, the minimum required for a majority, alongside one independent member who votes with them.
In the Senate, Republicans hold 53 seats. Democrats need 51 seats to take control of the chamber, accounting for tie-breaking votes cast by the vice-president.
If Democrats regain control of either chamber, they would have the power "to bring their own laws to the floor".
What issues are driving voters?
The economy and inflation are among voters' main concerns, particularly the rising costs of fuel, groceries, housing and healthcare. Inflation remains above target, influenced in part by "the war that the US and Israel started with Iran in February" and trade tariffs.
Immigration is another major issue. Republicans are emphasising tighter border controls and a "widespread – and often controversial – crackdown on illegal immigration".
Artificial intelligence regulation has also emerged as an area of debate. Senior politicians from both parties have called for regulation, "setting themselves in opposition to Trump, who has rejected the idea of laws to control development of the technology".
How could the results affect Trump's presidency?
The party of the incumbent president has historically tended to lose ground in midterm elections. Trump began his second term with an approval rating just above 50%, but the figure subsequently fell to approximately 37%, while 61% of respondents expressed disapproval.
If Democrats win control of either chamber, Trump "will find it difficult to get any laws through Congress". Democratic committee chairs could also launch investigations into "corruption allegations, the new White House ballroom and ICE tactics".
The prospect of impeachment is also being debated within the Democratic Party.
If Republicans retain control of both chambers, Trump will be able to "keep going with his plans for the remainder of his time in office".
What do the elections mean for 2028?
Although Trump cannot run for a third term, the midterm results will help shape the political landscape ahead of the 2028 presidential election.
The outcome could influence the positions of both parties and prompt early speculation about potential candidates for their presidential nominations.
The elections will therefore determine not only the balance of power in Congress but also the political conditions under which Trump governs for the rest of his presidency and the direction of the next presidential race.