About 240 million people are eligible to vote in this year’s US election, but only a relatively small number of them are likely to settle the question of who becomes the next president.
Experts believe there are only a handful of states that could plausibly be won by Kamala Harris or Donald Trump, for the Democrats or Republicans respectively.
Seven of them – Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin – hold the keys to the White House.
Now, in the final months of the election, both campaigns are at full throttle to win over undecided voters in these states.
Arizona
The Democrats gained the presidency in 2020 with the support of the Grand Canyon State, which narrowly voted to back their party’s candidate for the first time since the 1990s.
This state borders Mexico for hundreds of miles, and has become a focal point of the nation’s immigration debate.
Border crossings have fallen in recent months from record highs, which have made the issue near the top of voters’ concerns.
Trump has repeatedly attacked Ms Harris’s record on immigration, because she was given a role by President Joe Biden in trying to 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 swing states closely matches the list of places where Trump-backed Republican officials tried to thwart Mr Biden’s win in the 2020 election.
In Georgia’s Fulton County, alleged election interference has landed Mr 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 Mr Biden in the state. Trump denies any wrongdoing, and the case looks increasingly unlikely to be heard in court before the election.
A third of Georgia’s population is African-American, one of the country’s largest proportions of black residents, and it is believed that this demographic was instrumental in Mr Biden flipping the state in 2020.
Some disillusionment with Mr Biden had been reported among America’s black voters, but the Harris campaign hopes to animate this constituency.
Michigan
The Great Lakes state has picked the winning presidential candidate in the last two elections. Despite backing Mr 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 Mr Biden was in jeopardy. But Ms 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 has called on Israel to finish its campaign over Hamas in Gaza, but “get it over with fast.
The Silver State has voted Democrat for the last several elections, but there are signs of a possible turnaround by the Republicans.
Recent averages published by poll-tracking firm 538 indicate that polls once showed Trump enjoying a wide lead over Mr Biden, but that advantage has shrunk since Ms Harris became the top of the ticket. 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 Mr Biden took the presidency, the post-Covid recovery has been slower in Nevada than elsewhere.
At 5.1%, the state has the 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.