US midterm results and exit polls: When will we know the election outcome and what are the states to watch?

The midterm elections mark two years since Donald Trump was elected President, and its results will be a barometer of how the people of the US think he is faring. In recent weeks birthright citizenship, the migrant caravan and the mail bomber have overshadowed debates and may spell trouble for the Republican party.

The midterm elections, which involve a combination of elections for the US Congress, governorships and local races, take place every two years.

Republicans currently control the House of Representatives and the Senate – the two chambers which make up the US Congress. But pundits are suggesting the Democrats might take control.

With all 435 seats in the House of Representatives and 35 out of the Senate’s 100 seats up for election, as well as 36 state governors, there are a lot of races to keep an eye on. 

And with Trump's approval rating hovering around 40 per cent, a lot could change. Here is our guide on the states to watch – and when we can expect to see results from them.

When does voting start and end?

People will take to the polls across the 50 states from 1pm GMT today, with polls closing from midnight GMT onwards. Below are the last polling times for each state.

• 19:00 EST (midnight GMT): Georgia, Indiana, Kentucky, New Hampshire, South Carolina, Vermont, Virginia

• 19:30 EST (00:30 GMT): North Carolina, Ohio, West Virginia

• 20:00 EST (01:00 GMT): Alabama, Connecticut, Delaware, Florida, Illinois, Maine, Maryland, Massachusetts, Mississippi, Missouri, New Jersey, Oklahoma, Pennsylvania, Rhode Island, Tennessee

• 20:30 EST (01:30 GMT): Arkansas

• 21:00 EST (02:00 GMT): Arizona, Colorado, Kansas, Louisiana, Michigan, Minnesota, Nebraska, New Mexico, New York, South Dakota, Texas, Wisconsin, Wyoming

• 22:00 EST (03:00 GMT): Iowa, Montana, Nevada, Utah

• 23:00 EST (04:00 GMT): California, Hawaii, Idaho, North Dakota, Oregon, Washington

• 01:00 EST (06:00 GMT): Alaska

When will we know the results and will there be an exit poll?

The votes will start to be counted as soon as the each polling station closes, which means results will trickle in over the early hours of the morning. We can expect a clear picture on what the elections mean for the country by 8am tomorrow (Wednesday 7th November) GMT, however it's likely that an exit poll (or numerous ones as they may be state by state) will be available shortly after voting closes.

Which are the seats to watch for the House of Representatives?

The number of seats each US state receives depends on its population size. California, the most populous state, has 53 representatives while seven states - Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont and Wyoming have just one representative.

The Republican Party currently controls the chamber with a 43-seat majority, but it is widely expected that the Democrats will gain control in the upcoming election. The current House has 236 Republicans and 193 Democrats, with six vacant seats. 

The Democrats need a net gain of 24 seats to win a majority, which is no small accomplishment, but the president's low approval ratings have given the party reason to hope. 

West Virginia

Donald Trump won West Virginia's 3rd district by 30 points. But it is the Democratic candidate running in the district, which has a long history of coal mining, that is gaining national attention. Richard Ojeda says he voted for Donald Trump in 2016, opposes universal background checks for gun buyers, and is pro-coal.

Mr Ojeda is running against Republican Carol Miller in the open-seat race after the incumbent Republican Evan Jenkins vacated the seat to run for the Senate. 

Polling suggests it will be a tight race between the two candidates, but analysts are keeping a close watch to see if a populist Democrat in a pro-Trump area is a winning formula.

Last polls for West Virginia close at 19:30 EST (00:30 GMT).

California

Republican Representative Mimi Walters is battling to keep hold of her seat against Democrat Katie Porter in the state's 45th district, Orange County. The number of registered Republicans in the county has consistently declined as its population becomes more diverse.

Ms Walters is one of seven Republicans representing districts in California which Hillary Clinton won in 2016. The Democrats need to take several of these in order to have a chance of regaining a majority in the House.

Pundits are viewing a win in this race as a sign they will do well across Southern California - picking up crucial Republican-held seats. Professor Larry Sabato from the University of Virginia’s Center for Politics has changed his prediction from 'leaning Republican' to a 'toss-up'.

Last polls for California close at 23:00 EST (04:00 GMT).

Minnesota

Minnesota's 8th district is considered one of the Democrats' most at-risk seats in November. It is a traditionally Democrat area - former president Barack Obama won the district twice but it swung heavily to Donald Trump in the 2016 election.

The seat is currently held by Democrat Rick Nolan but the 74-year-old is not seeking re-election. The party's candidate Joe Radinovich, a former state legislator, is facing a tough battle against Republican Pete Stauber, a county commissioner.

Last polls for Minnesota close at 21:00 EST (02:00 GMT).

Texas

The race in Texas' 23rd district will largely focus on one of the Trump administration's main concerns - immigration. The district contains a third of the US-Mexico border and has the second highest population of 'Dreamers' - the term given to undocumented migrants who arrived in America as children and have been granted temporary protection.

The incumbent, Republican Will Hurd, is a former CIA agent who has chosen to distance himself from Mr Trump. His Democratic rival, Gina Ortiz Jones, is a Filipina-American, openly LGBTQ and an Iraq veteran. 

Mr Hurd, who became the first African-American elected to Congress from Texas when he was elected in 2015, is tipped to win by a narrow margin in the swing district. 

He has distanced himself from the national Republican party and even wrote an op-ed for the New York Times in July stating that the president had been manipulated by Russian intelligence.

Last polls for Texas close at 21:00 EST (02:00 GMT).

Florida

Moderate Republicans will be looking to Florida's 26th district to see whether they can keep hold of a largely Hispanic area in the Trump era.

The incumbent, Carlos Curbelo, is well-liked but Republicans still fear his Democrat opponent, Latin immigrant Debbie Mucarsel-Powell, could sweep to a surprise victory. Hillary Clinton won the district by 16 points in 2015.

Last polls for Florida close at 20:00 EST (01:00 GMT).

What about the Senate?

The US Senate is the upper chamber on Capitol Hill. There are 100 Senators, two from each state, and Republicans currently hold a razor thin majority with 51 seats.

The US Senate writes and passes laws but has a number of other powers and responsibilities, from ratifying treaties with other countries to overseeing investigations of officials and public bodies.

Senators have six-year terms and just 35 seats are up for re-election. Most of these are currently held by Democrats, making it hard for them to make gains. 

Nevada

Senator Dean Heller's election fight is an interesting one to watch. He is the only Republican senator up for re-election in a state that Hillary Clinton won in 2016. 

Senator Heller's Democratic opponent, Congresswoman Jacky Rosen, has also support from anti-Trump female voters. She is also hoping Nevada's growing Hispanic population will help her to victory in November.

However she faces an uphill battle in encouraging voter turnout, and Republicans are relying on white rural voters to come out to support Mr Heller.

Last polls for Nevada close at 22:00 EST (03:00 GMT).

North Dakota

Senator Heidi Heitkamp, who is facing re-election in a state Mr Trump won by nearly 40 points in 2016, is considered the most endangered Democrat in the Senate.

Ms Heitkamp will face pressure from conservative voters if she votes against Brett Kavanaugh's Supreme Court nomination, as she has suggested she will. However Ms Heitkamp has touted her previous support for Mr Trump's first Supreme Court pick, Neil Gorsuch, last year.

Her opponent, Kevin Crammer, also has the backing of the president. Mr Trump headlined a fundraiser for the Republican in early September which brought in more than $1 million in donations to his campaign.

Last polls for North Dakota close at 23:00 EST (04:00 GMT).

Florida

The race between Democratic Senator Bill Nelson and his Republican challenger Rick Scott is one of the most expensive of the year. Mr Scott, Florida's governor, has challenged Mr Nelson's record in Washington and distanced himself from the president so as not to lose out on Puerto Rican voters.

Republicans see the seat as one of their most promising chances of picking up an extra Senate seat and have spent heavily in the race. Polls show the two almost neck and neck - an interesting race to tune into on election night.

Last polls for Florida close at 20:00 EST (01:00 GMT).

Texas

Despite being a presidential candidate in 2016, Republican Senator Ted Cruz is now fighting for his political life in Texas. His Democratic challenger  - Bete O'Rourke - has brought Mr Cruz's lead in the deeply red state down to single digits, shocking political pundits.

Mr Trump has overcome his previous animosity with the Senator to lend his support to his campaign. Donald Jnr has already been deployed to campaign for Mr Cruz and the president himself may make an appearance in a bid to bolster support.

Mr O'Rourke, a 45-year-old congressman, has campaigned on a platform of inclusion and optimism, particularly on issues such as immigration. It is a message that chimes with the state's growing Hispanic population, which currently stands at 39 per cent.

Pollsters still predict a Cruz victory but Mr O'Rourke's popularity and upbeat campaign rallies have left Republican operatives deeply troubled.

Last polls for Texas close at 21:00 EST (02:00 GMT).