With 154 seats declared, the Democrats are up four.

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"We feel very comfortable about where we are," White House spokeswoman Sarah Sanders told Fox News.

Sanders told voters to look at races where Trump intervened by holding rallies, including in Tennessee where Republican Marsha Blackburn is projected to win re-election.

She forecasted that tomorrow, "a lot of the credit will go to the president, who campaigned for them".

Sanders also credited Trump with helping to secure a Republican Senate win in Indiana by holding a rally there, which she said, "close the deal" for challenger Mike Braun.

Anthony Zurcher
BBC North America reporter

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Democrats always faced an uphill fight in the Senate, with 10 incumbents running in states that Donald Trump carried in 2016. Even though the president won Indiana by 16%, Joe Donnelly was supposed to be one of the endangered candidates with a better chance to hold on.

Instead, he was the first to fall.

Mr Trump barnstormed the critical Senate battleground states in the final days of the campaign, effectively making the contests as much about him as they were about the individual candidates. It appears to have been an effective strategy in places like Indiana and Tennessee, an open Republican-held seat where Republican Marsha Blackburn staved off what could have been serious challenge by former Governor Bredesen.

In West Virginia, however, Joe Manchin continued to defy political gravity by holding onto his seat. And in other previously Trump-friendly 2016 states - Wisconsin, Ohio and Pennsylvania - Democratic incumbents breezed to victory.

In all, it makes for a muddled picture that as much reflects regional identities, demographic differences and specific candidate strengths as it does Mr Trump’s political power.

It also, however, nearly closes the door on Democratic hopes to retake the Senate. In a best-case scenario, a political tailwind would push all the at-risk candidates across the finish line. Instead, some survive while others falter.

Follow along for Anthony's live analysis here.

It's still very early in the night, and many key races are simply too close to call. But here's how things stand right now.

Indiana resident Karen Vaughn reveals why an absentee ballot mix-up won't stop her from voting this year.

Image source, Reuters

Democrat Joe Manchin is projected to hold his seat as a senator for West Virginia, defeating Republican Patrick Morrissey.

Donald Trump won West Virginia by a landslide in 2016.

Known for toeing the line between parties, Manchin notably voted to confirm President Donald Trump's nominee Brett Kavanaugh to the Supreme Court - the only Democrat to do so.

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Republican Senator Marsha Blackburn of Tennessee is projected to win her bid for re-election, narrowing the chances of Democrats winning a majority in the Senate.

Last month, Tennessee popstar Taylor Swift broke her political silence to endorse Democrats, including Blackburn's challenger Democrat Phil Bredensen.

The latest count has Blackburn with 61% of the vote to Bredesen's 36%, according to the Associated Press.

You can follow all live results here:

US mid-term election results 2018

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Democratic Sen Bob Menendez is projected to win re-election against Republican Bob Hugin in New Jersey, according to CBS News.

Menendez, who was accused by the US Department of Justice of accepting bribes, was found not guilty of using his office to perpetrate fraud in order to benefit a friend.

But the trial cast a long shadow over his campaign.

In a state with nearly one million more Democratic voters than Republican, incessant negative adverts saturated airwaves, reminding residents of last year's scandal.

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Indiana Republican Mike Braun has defeated incumbent Democrat Sen Joe Donnelly.

The race had been neck-and-neck and was seen as a toss-up by pollsters.

But Indiana is a state that has reliably supported Republican candidates in the past, and Trump won Indiana handily in 2016.

Donnelly's loss is considered a massive setback for Democrats angling to make gains in the Senate.

It's 21:00 and polls in Arizona, Colorado, Kansas, Louisiana, Michigan, Minnesota, Nebraska, New Mexico, New York, North Dakota, all of Texas, Wisconsin and Wyoming have now closed.

The races to watch in this region include:

In North Dakota, Heidi Heitkamp is up for re-election and is a vulnerable Democrat.

In Arizona, Republican Jeff Flake's seat is up for grabs - and both candidates are women.

Incumbent Republican Andy Barr has been re-elected to the House of Representatives by his Kentucky district.

It was a toss-up race many were watching closely to get a sense of how worried Republicans should be.

Barr defeated Democrat Amy McGrath, a retired Marine fighter pilot.

Anthony Zurcher
BBC North America reporter

Image source, Getty Images

Our correspondent Anthony Zurcher will be providing analysis updates as election results start to trickle in.

Here is his latest breakdown as of 20:45 EST (01:45 GMT):

If a Democratic wave election is coming, Virginia congresswoman Barbara Comstock was always going to be the one the first to disappear beneath the deluge. Her defeat, which was announced relatively quickly, wasn't a big surprise. But it's also one of the first data points to suggest that Democrats are doing what they have to do to take back the House of Representatives.

The southern Miami district that had long been the home of Republican Ileana Ros-Lehtinen was expected to be another easy pickup for the Democrats - and it was. Hillary Clinton beat Donald Trump there by 20% in 2016.

And though the Republican, charismatic young Spanish-language television host Maria Salazar, ran a strong race against former Clinton administration health secretary Donna Shalala, even the best candidates can't hold back the tide in districts with such a decided partisan tilt.

Read more of Anthony's live analysis here:

Mid-term election results: Key takeaways so far

The BBC's Gary O'Donoghue is at Ted Cruz's election headquarters in Texas, where some "true Texans" are beginning to show up.

With barely 1% of precincts reporting, challenger Democrat Beto O'Rourke and Cruz remain in a tight race.

It'll be another few hours before the picture there begins to become clear.

Incumbent Democratic Sen Sherrod Brown has been re-elected in Ohio, CBS projects, a state that President Trump won by a margin of eight points in 2016.

Brown, who is also considered a possible presidential contender, faced Republican Jim Renacci, who entered the race after State Treasurer Josh Mandel unexpectedly dropped out of the race.

Google has mapped live searches related to the election in this attractive tool.

It shows trends in Americans googling information about issues like voter intimidation and voting machine problems.

In California, searches about provisional ballots have increased in the past hour - voters can be asked to complete a provisional ballot if their voter eligibility is in question.

And in Georgia, searches about long waiting times are peaking, confirming reports about high voter turnout in the state.

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As we wait to see poll numbers trickle in, take a look at what could happen via a choose-your-own-adventure, mid-terms style.