Image source, Getty Images

Around 1,000 election monitors and observers are being deployed to all 50 states for the first time in US history, says the US Department of Justice (DOJ).

The monitors will be used to check federal voting laws are being followed in support of "free and fair elections", according to the DOJ.

Previous administrations have monitored elections in this way but not on the same scale.

During the 2022 midterms, the DOJ under President Biden sent monitors to 24 US states.

Samira Hussain
Reporting from Des Moines, Iowa

Polls have opened here in Des Moines, Iowa where Democrats are hoping to flip this reliably red state, blue.

This election is a referendum on President Donald Trump's second term in office.

Trump is not on the ticket but has been urging his supporters to vote as if he was.

But many people are dissatisfied, citing the economy and the high cost of living as the main issues.

Democrats have been laying the blame for the country's economic woes with the current administration. Republicans have been countering that message, saying a vote for Democrats is a vote for radicals and extremists.

Already 58 million Americans have cast a ballot in early voting across the country, a record turnout for a midterm election.

Polls have just opened in Iowa, Alabama, Kansas, Oklahoma, South Dakota, Texas,Wisconsin, Arizona, Mississippi, North Dakota.

Now, we wait on the rest of the country as polls in Hawaii, for example, will only open at 13:00 eastern (18:00 GMT).

Election officials in Florida are temporarily relocating 19 polling stations because of flooding across the state.

On Monday, Florida Governor Ron DeSantis issued an executive order declaring a state of emergency in multiple counties.

The order allows election supervisors to change polling stations when the original sites become unsafe or inaccessible to voters, according to the BBC's US news partner CBS.

Florida's Division of Emergency Management says it's providing pumps, generators, and other resources to flood affected areas across the state.

Image source, Forida Division of Emergency Management/ X

Bernd Debusmann Jr
White House reporter

Image source, Reuters

As the weeks and months of midterm campaigning have gone on, Trump has repeated a plea to voters in nearly every campaign rally: "Pretend I'm on the ballot."

Trump, essentially, is hoping for a repeat of the 2024 presidential election, in which the personal loyalty of millions of voters – and dissatisfaction with President Joe Biden and the Democrats – swept him and the Republicans back into the White House and control of Congress.

The president, however, is not on the ballot and his career in formal politics will come to an end at the end of his term. His strategy – attempting to nationalise thousands of local and state elections – is an unusual one.

Clearly, he believes that voter enthusiasm for him, personally, will carry Republican candidates to victory and stop what he has repeatedly acknowledged is a historical trend in which incumbent parties take a drubbing in the midterms.

Polling day has just begun but many early birds have already cast their votes.

Image source, Reuters

Image source, Reuters

Image source, Reuters

Image source, Reuters

Republicans currently control both the House of Representatives and the Senate.

Polls suggest Democrats could win a majority of seats in the House.

But the race for a majority in the Senate is much less certain. These are the key states that will decide which party is in charge for the next two years:

• Alaska: Republican Dan Sullivan's re-election bid is being challenged by Democrat Mary Peltola and independent candidate Daniel J Sullivan
• Maine: Susan Collins is running for a sixth term against Democrat Troy Jackson
• Texas: No incumbent is in this race, setting up a highly anticipated contest between Democrat James Talarico and Republican Ken Paxton
• Kansas: Megachurch pastor Adam Hamilton is the Democratic challenger to incumbent Republican Roger Marshall in an unexpectedly close race to represent a state that for decades has reliably voted Republican
• Michigan: With no incumbent in the race, Michigan's race is among the most closely watched. Democrat Abdul El-Sayed could become the first Muslim US senator, but he faces a strong challenge from Republican Mike Rogers

For more stories from the US and around the world, follow BBC News US on WhatsApp.

Polls have just opened in Florida, Delaware, Georgia, Illinois, Louisiana, Maryland, Massachusetts, Michigan, Missouri, Pennsylvania, Rhode Island, South Carolina, Washington DC.

Individual state governments decide on what time their polls open.

A little earlier, polling stations opened across the east coast - including in swing states Maine and Ohio.

As polls are opening across the US, some 58,677,062 votes have already been cast, as of 23:30 eastern time (04:30 GMT) on Monday.

According to data published by the Election Lab at the University of Florida, 31,897,521 were in-person early votes and 26,779,541 were mail ballots.

More US states have offered early voting in recent years. The Center for Election Innovation & Research says that 97% of eligible voters in the US live in areas where this is an option.

Image source, Reuters

Jack Grey
Live reporter

Image source, Getty Images

Democratic Congresswoman Haley Stevens has defended her decision to endorse the Republican candidate for the key Senate seat of Michigan, Mike Rogers.

Stevens, who lost out on the Democrat nomination to El-Sayed, has been heavily criticised by members of her party for the move.

In an 890-word post on X last night, Stevens ran through her reasons for endorsing Rogers, including:

• Political ads: Stevens identifies attack ads on Mike Rogers, both unofficial and from the El-Sayed campaign, which she says are not the way to "bring people together"
• Hasan Piker: She criticises El-Sayed's association with the left-wing political commentator and streamer
• 'Shut out': Stevens says she was told she was not welcome at El-Sayed's campaign events, which, she says, raises questions as to how he can "represent an entire state filled with people who disagree with him"

Sakshi Venkatraman
US reporter

The political party that controls Congress has the power to shape the laws of the US – laws that affect Americans from coast to coast.

Currently, Trump's Republican Party has power in the White House and both chambers of Congress – the House and the Senate. Their majority is slim, but it means they have the power to bring their preferred laws to the floor and have them signed off by the president.

The Democratic Party opposition wants to change that.

It's now 06:30 in North Carolina, Ohio and West Virginia and polls have just opened.

While results won't come in until much later, Ohiois on our list of US Senate races to watch closely in these midterm elections.

It's just gone 06:20 US eastern time and voters are beginning to spill into a sports hall in Manchester, New Hampshire, to cast their ballots.

Image source, Reuters

Image source, Reuters

Sarah Smith
North America editor

Image source, Getty Images

With two years of his presidency remaining, Donald Trump, who has dominated American politics over the past decade and transformed it in remarkable ways, is facing potentially pivotal elections.

Voters overwhelmingly say they are most concerned about the cost of living. Food and fuel prices have soared in part due to the president's aggressive tariffs and unpopular war with Iran, so it will be top of mind as many head to the polls.

Trump, who has faced record low approval ratings in recent months, has been campaigning hard, headlining dozens of rallies across the country.

But high prices are a concern for voters on all sides – which helps explain why he has been campaigning in previously safe Republican territory, appearing in Iowa and Kansas during a final weekend blitz.

His party has also poured hundreds of millions of dollars of campaign advertising into these traditionally safe contests, such as the Senate race in Kansas.

• The BBC's North America editor Sarah Smith has more analysis ahead of today's pivotal elections

• First results: Start to come in after 18:00 EST (23:00 GMT). They won't tell us much about the overall picture because these races are in places considered safe bets
• Possible early indications: There are several tight Senate contests in the eastern time zone - like Ohio, where polls close at 19:30 EST (00:30 GMT) and Maine,where they shut at 20:00 EST (01:00 GMT). Thesecould provide early indications of the electorate's mood
• "Calls" and projections: Some key contests might start to be "called" by US media outlets using models. But in some closely-fought states, outlets could take a long time to make their projections
• Overall result: The overall timing of the result will depend on how tight the races are and which races end up being decisive

And a word of caution – in 2022, Republicans and Democrats were still in a tight race for control of the US Congress on 9 November, a day after the midterms.

Kwasi Gyamfi Asiedu
Live reporter in Washington

Image source, Getty Images

It's 6:00 here on the US east coast and polls have now officially opened in states up and down this region, including New York, New Jersey, Virginia, Maine, and Kentucky.

Polls opened an hour ago in Vermont, while voters in North Carolina, Ohio, and West Virginia can begin voting in half an hour.

As more polls open across this vast country, voters will be selecting candidates in highly consequential elections that will decide the balance of power in the US Congress as well as the governorship of some states.

The results from today will have ramifications far beyond this country.

Stay with us as we bring you more from our correspondents nationwide and hear from everyday Americans about what matters to them as they enter the voting booths.

Image source, Reuters

As we've been reporting, the Iran war – deeply unpopular with many voters – hangs over the midterm elections.

In the latest development, the US launched strikes on Iran’s Qeshm Island in the Strait of Hormuz on Monday.

Iranian state news agency IRNA reported several explosions on the island.

US officials described the strikes as limited and said they were in response to Iran's Islamic Revolutionary Guard Corps (IRGC) firing on a US aircraft.

Lyse Doucet
Chief international correspondent

Opinion polls show Donald Trump's war in Iran is deeply unpopular.

His gamble sent prices soaring, and sparked protests from Democrats and Republicans too that he’s waging war without permission from Congress.

And there's no sign the vital Strait of Hormuz will open soon. Diesel and gasoline, food and fertiliser – they're all affected.

When the US, backed by Israel, went to war in February, they said it would all be over within four to six weeks. Trump proclaims "one of the greatest things we’ve done" is stop Iran from acquiring nuclear weapons.

US strikes on its nuclear sites in 2025 inflicted significant damage. But this year’s on-off talks made little progress.

Despite tactical success in destroying parts of Iran’s arsenal, Trump's war is widely regarded as a strategic failure; it has only hardened and emboldened its leaders.

And Americans will cast ballots amid reports another escalation is on the agenda.

Image source, Getty Images

Image source, Barack Obama / X

Following weeks of campaigning in key battleground states for the Democrats, former US President Barack Obama said people were fed up of life under Donald Trump's Republicans and were ready for something different:

He made those comments on X, external on the eve of Tuesday's polls, highlighting the senate races in the key states of Georgia, Ohio and Michigan.

The midterms will be seen by many as the final voter verdict on Trump before his term ends in 2028, setting the scene for the rest of his premiership.

So what's he got to gain – or lose?

Our North America correspondent Anthony Zurcher explains.