What time do the polls close and when will midterms results be announced?

Adam Gabbatt in New York

Tuesday’s midterm elections will shape the future of US politics over the next two years. The key question in these elections is: will Republicans be able to keep control of both chambers of Congress?

Historically, the party of the president has lost seats in the House of Representatives in midterm elections. In 2010, two years after Barack Obama was first elected, Democrats lost 63 seats in the House.

But polling suggests Democrats are unlikely to win the Senate – and may even lose seats.

In the House, Democrats need to flip 23 Republican-held seats to take control, which would restrict Trump’s ability to act on some of his key election promises, like the border wall. It would also be a major embarrassment to Trump, given he has spent months campaigning for Republicans around the country. Trump’s miserable approval rating – 42% – gives Democrats reason to be hopeful.

As well as a potential late-night Trump Twitter meltdown, there’s plenty more to watch out for on Tuesday. More women are running in the midterm elections than ever before, and three states could elect African American governors for the first time.

When do the polls close?

Most polling places will close between 7pm ET and 11pm ET. But in Alaska and Hawaii most will shut at midnight ET. Of the states with earlier closures, Florida, Pennsylvania and New York have a number of House seats which Democrats consider winnable.

When do exit polls come out?

Early – as soon as the polls close. But remember 2016? Once convinced a Democrat is going to win, twice shy. So it’s best to wait until actual results come in.

When can we expect results?

It won’t be straight away. The size of some states, the high number of absentee ballots, the predicted high turnout at the polls, and the expected closeness of some of the races all mean that many results won’t come out until the small hours of Wednesday morning at the earliest.

But given that some key districts should be called relatively early in the evening, we could have an idea of who will control the House by midnight. In the 2014 midterms the Associated Press called the Senate for the GOP at 11.25pm.

That means there is likely to be a tense wait before we know who will control the House, in particular, for the next two years.

In 2014 it took two weeks for California to announce the winners of two House elections. And then there is the added complication of some states requiring the winner to get more than 50% of the vote. If they don’t, the top two candidates enter a runoff, and people have to vote all over again.

How to follow

The Guardian will be live-blogging all night and throughout the next day. We’ll have up-to-the-minute information on results and updates from our correspondents in all the key districts.

ABC News, CBS News, C-Span, and PBS all plan to broadcast live coverage, while NPR will be live from 8pm ET. Of the cable channels, CNN and MSNBC will have chin-stroking gurus poring over maps of the US, while Fox News will boast typically considered coverage featuring Tucker Carlson, Sean Hannity and Laura Ingraham.

Races to watch: the House

As of Friday the Cook Political report rated 17 Republican-held seats as likely to flip to the Democratic party, or leaning towards the Democrats.

Some of the races attracting attention include Sharice Davids, a Kansas lawyer and former MMA fighter, who would become one of the first Native American women elected to Congress. (Deb Haaland, who is also Native American, could win election in New Mexico.)

In New York’s 19th district Republican incumbent John Faso is running neck-and-neck in the polls with Antonio Delgado. The campaign has been marked with racist overtones, as GOP groups have used loaded attacks against Delgado, who is African American, over his former rap career.

Steve King, a long-serving Iowa Republican, could lose his re-election bid. King, known for his inflammatory beliefs and statements, has plunged in the polls as attention has been drawn to his relationships with European far-right parties and endorsement of politicians with ties to neo-Nazi groups.

Races to watch: the Senate

Republicans have their eyes on Montana’s Jon Tester, a former farmer, in a state which Trump won by 20 points in 2016. Heidi Heitkamp, Democratic senator for North Dakota, is also vulnerable.

Many are following Democrat Beto O’Rourke in Texas, who is hoping to oust Republican Ted Cruz – a 2016 presidential candidate – from the Senate. O’Rourke has drawn large crowds, and plenty of press attention, but is running behind Cruz in the traditionally red state.

Races to watch: governors

If elected, Stacey Abrams, Andrew Gillum and Ben Jealous would become the first African American governors of Georgia, Florida and Maryland.

Abrams and Gillum, who has faced racially charged comments from his opponent, are in tight races, while Jealous – a progressive backed by Bernie Sanders – looks to be more of a long shot.

In Vermont, the Democratic candidate Christine Hallquist would become the first ever transgender governor if she defeats Phil Scott, but is behind in polling.