Thomas Sparrow
BBC Mundo, Washington

At this polling station in Columbia Heights, a neighbourhood in Washington with a large number of Hispanics, many people I spoke to stressed the need for comprehensive immigration reform. Leticia Arias, who arrived to the US from Mexico nearly 30 years ago, said she was disappointed in President Obama because she voted for him twice and there is still no reform. "To this date there is no solution and we have waited a long time", she said.

Kyle Stephenson, an accountant, told Reuters he had recently switched political parties from Republican to Democrat, citing widening economic inequality.

"It seems like the gap between the really rich and the rest of us is just getting bigger and bigger... It's gotten harder and harder for regular Americans to make a living."

Jon Sopel
North America editor

tweets, external: Interesting exit poll data emerging. Seems to add up to this: voters don't much like #Obama nor the #GOP - #BBCMidterms #plagueonyouall

North Carolina set a record this year as the most expensive Senate race in US history; $113m has been spent on the race, shattering the previous record of $77.3m set in 2012. Outside group spending totalled $81m, dwarfing the $32m raised and spent by the two candidates.

This year will go down as the most expensive mid-term election in US history. Why? The short answer is because there's been a flood of money from outside groups - rich billionaires, corporations and special interests. Twenty-three percent of all spending this cycle has come from groups not connected candidates or political parties.

ABC News Politics

tweets, external: Conn. judge orders 2 voting locations in Hartford to remain open until 8:30 p.m. ET after claims that some polling stations opened late.

This sums up the mood of many Americans. Emily Conover, a saleswoman from Elizabethtown, Kentucky, told the Associated Press news agency she voted for Democratic challenger Alison Lundergan Grimes over Senate Minority Leader Mitch McConnell, but she "didn't really like either of them".

Here's a very nifty video explainer on how the Republicans can win the Senate - all in 100 seconds, from The Washington Post, external.

Polls close in some eastern states of the US in under 90 minutes. And once the voting stops the counting starts.

From 0000 GMT you can follow the vote count live via our interactive results map. The Associated Press will provide data for every House, Senate and Governor race as well as key ballot initiatives.

Just click to see the state of every race in real-time - right down to the number of votes each candidate has in a precinct.

What happens if Republicans only gain five seats in the US Senate, making it an even 50-50? By procedure, the tiebreaker goes to Vice-President Joe Biden, effectively retaining Democrat control.

Image source, AP

And more voters - 54% versus 44% - disapprove than approve of President Barack Obama's job performance as president, according to that preliminary ABC exit poll.

According to a preliminary ABC exit poll, voters by 65%-31% say the country is heading seriously on the wrong track rather than in the right one.

Aleem Maqbool
BBC news, Iowa

Image source, Reuters

In Iowa, farmyard animals have played a surprising but perhaps decisive role in what remains a knife-edge battle. The relatively unknown Republican nominee Joni Ernst grabbed attention across America with an advert focused on rural values.

"I'm Joni Ernst. I grew up castrating hogs on an Iowa farm, so when I get to Washington, I'll know how to cut pork," she said. The sentiment clearly struck a chord with many in this largely agriculture-dependent state, such that the latest opinion polls show a race that is now simply too close to call.

US turnout during mid-term years is comparative to turnout in Colombia and Pakistan, according to the International Institute for Democracy . And it is far below countries like Denmark and New Zealand - all without compulsory voting. Recent elections in Tunisia saw 65% of eligible voters cast ballots, the first election under a new constitution.

Turnout could be a factor. Low mid-term voter turnout generally favours Republicans, because mid-term voters are generally older and have a higher education level. Democrats have a lower voting registration rate.

Tara McKelvey
BBC News, Kansas

Harlan Brush, an ex-racing car driver in Topeka, Kansas, says Republican Senator Pat Roberts, who is in a tight race with independent Greg Orman, "doesn't have a clue".

The fact that Congress is currently split - with each party controlling a chamber - means voters don't know who to blame for the legislative gridlock, say analysts. Or maybe it's because they don't actually know who does control the House and Senate.

The vast majority of Americans may disapprove of the job Congress is doing, but in recent years 90% of incumbents have been re-elected. This odd fact has a name - the Fenno Paradox - named after political scientist Richard Fenno.

Rajini Vaidyanathan
BBC News, Washington

tweets, external: West Virginia predicted to elect first Republican Senator in more than 50yrs.

Job approval for Congress is at an all-time low, just 14%, and the last session of Congress was described as the least productive on record, in terms of bills passed.