Americans are voting on Tuesday in midterm elections that will decide control of Congress and are widely seen as a referendum on Donald Trump's second presidency.

Both chambers are currently held by Republicans, and the outcome will determine whether the president can legislate freely in his final two years or faces a divided government. The Guardian reported that control of the Senate and House of Representatives is at stake, with Democrats hoping to win back at least one chamber.

The campaign has been dominated by Trump, who has staged dozens of rallies across the country and used his closing pitch to argue that Republicans "gave this a very strong shot". He spoke on Monday in front of the Reflecting Pool in Washington DC, a site that has itself been the subject of a controversial renovation project.

The economy is the issue

Voters overwhelmingly say they are most concerned about the cost of living. Food and fuel prices have soared in part because of the president's aggressive tariffs and an unpopular war with Iran, putting affordability at the centre of almost every competitive race.

That is an uncomfortable position for an incumbent party. Trump has faced record low approval ratings in recent months, and his campaign schedule reflected it: he spent the final days in Iowa and Kansas, territory that would normally be safe for Republicans.

The closing argument from Republicans has focused on immigration and on the argument that a Democratic Congress would raise taxes. Democrats have focused on prices, healthcare costs and on the president's use of executive power.

What to watch on the night

Control of the House is expected to be decided by a relatively small number of suburban districts, many of them in states where early voting has been heavy. Control of the Senate runs through a handful of races that polls suggest are close, including in states where the cost of living has risen fastest.

Early voting has been heavy in many states, and election officials have warned that counting could take days in places where mail ballots are processed after election day. That is why the timing of a result may matter as much as the result itself: a slow count in a close race invites claims of fraud, and both parties have spent the campaign preparing their supporters for that possibility.

Turnout in the closest districts, rather than the national totals, will decide the outcome, and both parties have been directing their final spending there. That is why the result may look inconsistent with the polls for a few hours before it settles. Some allow mail ballots to be processed as they arrive; others wait until election day, which means a long night and a longer week in the closest races. In 2020 and 2022, the pattern of in-person votes being counted first produced shifts in the leads overnight, and the same is likely again.

Results may not be immediate. Several states count mail ballots over days, and close races could trigger recounts or legal challenges. The lesson of recent cycles is that the winner may be known long before the final tally, or may not be known for weeks.

Why it matters beyond America

The elections will shape US policy on tariffs, Ukraine, Iran and AI regulation, all of which have consequences far beyond the country's borders. A Congress controlled by one party or split between two produces different answers to each.

For markets, the immediate question is whether a divided government means stalemate or stability. For allies, it is whether American commitments hold. For voters, the question is simpler and more immediate: whether prices stop rising.

Trump has said he expects Republicans to do well, despite the polls and the approval numbers. The ballots being counted on Tuesday will test that claim more directly than any survey.

The structural backdrop matters as much as the campaign. The president's party has historically lost seats in midterm elections, and this cycle began with narrow Republican majorities in both chambers, which leaves little room for error. A single net loss in the Senate can flip control, and a handful of House districts decide the majority.

If Democrats win one chamber, the practical effect is not a reversal of the president's agenda but a brake on it: committees gain subpoena power, spending bills need negotiation, and nominations slow down. If Republicans hold both, the president's final two years look very different, with room to legislate on tariffs, immigration and AI policy.

Counting will take time. Several states process mail ballots over days, and close races can lead to recounts and litigation. The result may be clear on Tuesday night, or it may take a week, and the difference matters for how the country reads the outcome, and for how quickly the next Congress can organise itself.

The vote follows record early voting, a final week of Trump's rallies in Iowa and Kansas, and an inflation report that framed the economic argument in our account of US growth and prices.