When will we know the US midterm election results?

On Tuesday night, the United States – and many people around the world – will be following one of the country’s most closely contested midterm elections in recent years.

All 435 seats in the US House of Representatives and 35 of the 100 Senate seats are up for grabs as Democrats hope to take control of both chambers from President Donald Trump’s Republican Party.

The first results should be known on Tuesday after polls begin to close. Voting will end first in some jurisdictions on the East Coast at 6pm (23:00 GMT).

Results will continue to come in throughout Tuesday evening, and some probably won’t be known until Wednesday or later in some races as more states finish voting and officials start releasing their vote counts.

But the first reported results won’t necessarily mean that a winner has been announced.

Election officials release vote counts as ballots are processed, and news organisations, like The Associated Press, then analyse them to determine how to call a race.

A closely contested race could take hours to call – or even days. It might not be clear for days whether the Republicans will retain control of Congress or Democrats secure a majority in either or both chambers.

The first polling stations to close will be in parts of Indiana and Kentucky.

Many races could be called on election night, but it might take several days to know which party will control the House and Senate in the final two years of Trump’s presidency.

If, for example, the US Senate race in Alaska requires a ranked-choice tabulation, the next round is scheduled for November 18.

So there is no specific deadline for knowing all the results. In races that are not close, news organisations are able to declare winners well before every ballot is counted while official certification takes place later. So quick reporting does not guarantee a fast race call.

In 2024, it took eight days to determine which party would control the House of Representatives.

If a race is very close, a recount might be triggered automatically or if requested by a candidate, depending on state law.

Candidates also have the option of challenging the results in court, which could also delay the final result.

Trump has also raised questions about whether he would accept the midterm election results. When he was asked if he would respect the final outcome, he said; “I will if there are honest elections.”

But the US president cannot overturn congressional election results simply because he disagrees with them. Elections are administered and certified by individual states, and legal challenges must follow a process.

“All the states run elections. Courts accept that states run elections,” Democratic strategist Mali Smith told Al Jazeera.

Under the US Constitution, the House and Senate have the final authority to judge disputes over the elections of their own members.

Depending on the dispute, recounts and legal challenges could take days, weeks or longer to resolve.