About 240 million people are eligible to vote in the 2024 US election, but only a relatively small number of them are likely to decide who becomes the next president.
Experts believe there are only a handful of so-called “swing” states that could plausibly be won by either Democrat Kamala Harris or Republican Donald Trump.
Seven of these – Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin – are thought to hold the keys to the White House.
Both campaigns have therefore been targeting undecided voters in these states.
The Democrats gained the presidency in 2020 with the support of the Grand Canyon State, which narrowly voted to back the party’s candidate for the first time since the 1990s.
Arizona
Arizona borders Mexico for hundreds of miles, and has become a focal point of the nation’s immigration debate, although the number of border crossings has dropped back in recent months from record highs.
Trump has repeatedly attacked Harris’s record on immigration, because she was given a role by President Joe Biden to try and ease the border crisis.
He has also vowed to carry out “the largest deportation operation” in US history if he regains the presidency.
Arizona has also hosted a bitter row over abortion access, after state Republicans tried unsuccessfully to reinstate a 160-year-old near-total ban on terminating pregnancies.
The issue has become even more polarising since 2022 when the US Supreme Court overturned a landmark ruling that gave women a constitutional right to abortion.
Georgia
Our list of key swing states closely matches the list of places where Trump-backed Republican officials tried to thwart President Biden’s win in the 2020 election.
In Georgia’s Fulton County, alleged election interference has landed Trump in one of his four criminal prosecutions (Trump has been convicted in one case, while the remaining are ongoing).
He and 18 others are accused of conspiring to overturn his narrow defeat to Biden in the state. Trump denies any wrongdoing, and the case will not be heard in court before the election.
A third of Georgia’s population is African-American – one of the largest proportions of black residents in the US – and it is believed that this demographic was instrumental in Biden flipping the state for the Democrats in 2020.
Some disillusionment with Biden had been reported among America’s black voters, but the Harris campaign hopes to gain their support.
Michigan
The Great Lakes state has picked the winning presidential candidate in the last two elections. Despite backing Biden in 2020, it has become symbolic of a nationwide backlash over the president’s support for Israel during that country’s war in Gaza.
During Michigan’s Democratic primary contest in February, more than 100,000 voters chose the “uncommitted” option on their ballots, part of a campaign mounted by activists who want the US government to halt its military aid to Israel.
Notably, Michigan has the country’s largest proportion of Arab-Americans – a demographic whose support for Biden was in jeopardy. But Harris has taken a harder tone on Israel, and some Gaza protesters have told the BBC they hope she will be more sympathetic to their cause.
Trump has highlighted the state’s significance in his potential path to victory. Commenting on events in the Middle East, he called on Israel to finish its campaign over Hamas in Gaza, but “get it over with fast.”
Nevada
The Silver State has voted Democrat for the last several elections, but there are signs of a possible turnaround by the Republicans.
Trump had enjoyed a wide lead over Biden in earlier polls, but recent averages published by poll-tracking firm 538 indicate that advantage has shrunk since Harris gained the nomination. Democrats had hoped a candidate with greater appeal to younger and more diverse voters would close the gap.
Both candidates are vying to win the state’s sizeable Latino population.
Despite the fact that the US economy has shown strong growth and jobs creation since Biden took the presidency, the post-Covid recovery has been slower in Nevada than elsewhere.
At 5.1%, the state has the third highest unemployment rate in the country, after California and the District of Columbia, according to the latest US government statistics.
If Trump comes to power again, he has vowed a return to an agenda of lower taxes across the board, and fewer regulations which could appeal to voters.
North Carolina
Polls appear to have tightened in the Tar Heel State since Harris took her place at the top of the Democratic ticket, and some analysts now call it a “toss-up”.
That may have explained Trump’s decision to hold his first outdoor rally there after the attempt on his life in July.
“This state is a very, very big state to win,” he told the crowd.
For their part, the Democrats decided to give a platform to the state’s governor, Roy Cooper, on the final night of their party convention.
North Carolina borders Georgia, and shares some of its top electoral concerns, as well as those in Arizona, another Sun Belt state.
Trump carried North Carolina in 2020 but did so by just over 70,000 votes, which has further buoyed Democrats’ hopes that this “purple” state (one that could vote red or blue) could be winnable in this election year.
Pennsylvania
The Keystone State is considered by some pundits to be the biggest prize on the electoral battleground map. It has been inundated with campaign stops from both Harris and Trump. The two candidates and their running mates have made more than 50 appearances there since mid-July.
Pennsylvania proved pivotal in the 2020 election, when it backed Biden. Along with Michigan and Wisconsin, it has been a key focus of Harris’s campaign.
Trump survived the first of two attempts on his life in Pennsylvania. He, too, has been campaigning there doggedly – and the state is at the centre of a controversial cash giveaway to voters by his supporter, Elon Musk.
The economy is a top issue here, as well as many other places. Inflation spiked across the country under the Biden administration, before gradually reducing.
Pennsylvanians are far from unique among Americans for feeling cost-of-living pressuresas a result of inflation. But the price of groceries has risen faster in their state than in any other, according to market intelligence provider Datasembly.
High inflation could hurt Harris across the US as polling suggests it has given voters an unfavourable view of the economy.
Trump has sought to attack his rival by pinning her to the Biden economy – despite the latest official figures showing annual growth of 2.8%.
Wisconsin
The Badger State picked the winning presidential candidate in both 2016 and 2020, by a margin of little more than 20,000 votes each time.
Pundits have suggested marginal states like Wisconsin are where the biggest impact could be made by third-party candidates who are campaigning against the policies of both the Democratic and Republication nominees.
Polling had indicated that a sizeable show of support for independent candidate Robert F Kennedy Jr could have harmed the vote tallies for Harris or Trump. Kennedy suspended his campaign in late August and endorsed Trump.
Democrats have been fighting to have Green Party candidate Jill Stein removed from the ballot in Wisconsin, saying the party did not comply with state election laws, and has also filed an elections complaint against Cornel West, a left-leaning academic.
Trump has described that state as “really important… if we win Wisconsin, we win the whole thing”. The summer Republican National Convention was held in Milwaukee.
Harris was rallying in that same city when her party’s own convention formally nominated her as the Democratic presidential candidate.
By BBC News