Campaigns for the United States are well underway, with tens of millions of voters due to turn out on Tuesday 5 November.
Seven swing states have been identified in the race between Democratic vice president and : Nevada, Arizona, Wisconsin, Pennsylvania, Michigan, North Carolina and Georgia.
Swing states are those that have similar levels of support for both candidates and could lean either way come election day.
Results in these states will likely decide the election and many will have razor-thin margins that could come down to tens of thousands of voters.
Why are these states so important?
Swing states are important because US presidential elections are decided by a voting system known as the Electoral College and not the popular vote.
The Electoral College is a weighted system where 538 electors decide the winner, with a majority of 270 electoral votes required to win the presidency.
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States each have the same number of electoral votes as they have representatives and senators — electoral votes do not correspond to population size in most states.
For example, in Wyoming, one electoral vote accounts for 195,000 people, but in Texas, Florida and California, one electoral vote accounts for over 700,000 people.
Associate Professor David Smith from the United States Studies Centre said the Electoral College was a controversial voting system, and increasing polarisation in the US meant that discrepancies between the popular vote and the Electoral College were more likely.
"Now we have some states that are overwhelmingly one side or the other that means you are never going to get these sweeping electoral college victories that you used to have, which reflected the popular vote," he told SBS News.
"You can have these situations where the loser on the popular vote can actually win the electoral college."
The electoral votes in Nevada (six votes), Arizona (11 votes), Wisconsin (10 votes), Pennsylvania (19 votes), Michigan (15 votes), North Carolina (16 votes) and Georgia (16 votes) are essential for victory in 2024.
A key factor that unites the swing states in this electoral cycle is that they all have large urban and rural areas, which creates a strong political divide. Source: Getty / Scott Olson
Are swing states always the same?
Swing states have changed throughout the history of US presidential elections.
The states considered swing states in this election cycle have been recognised as such for several election cycles but other states used to be major points of focus.
For example, Missouri was once considered a key swing state that Democratic candidates needed to win to secure the presidency, however, in 2008 Barack Obama became the first Democrat to be elected without the state.
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Smith said most states have historically changed allegiance between the Democratic and Republican parties quite routinely.
"I think a good historical thing that explains this is in 1984, Ronald Reagan won 49 of the 50 states — the one that he missed was Minnesota. In 1964, Lyndon Johnson won 44 out of the 50 states," he said.
"That means that there aren't any states that have had a consistent record of voting for the same party that goes back more than a few decades because you've got these electoral wipe-outs on both sides."
The seven swing states are overwhelming the focus of campaign events and advertising for Kamala Harris and Donald Trump. Source: Getty / Jeff Swensen
What's unique about swing states?
Smith said that a key factor that unites the swing states in this electoral cycle is that they all have large urban and rural areas, which creates a strong political divide.
"In all these states, you've got one or two big cities. Milwaukee and Madison in Wisconsin, Detroit in Michigan, Philadelphia and Pittsburgh in Pennsylvania, Atlanta in Georgia, Phoenix in Arizona, and Las Vegas in Nevada. And then you've got a lot of rural areas, which are overwhelmingly Republican," he said.
Smith said states where Democrats win consistently have a significantly larger urban population, including California, New York and Illinois. Whereas states with large rural populations, such as Wyoming, Alabama and Missouri, have become reliably Republican.
How have Kamala Harris and Donald Trump campaigned in these states?
Swing states are overwhelming the focus of presidential campaigns, with nearly all campaign events held in these states.
In addition to frequently hosting rallies, Harris and Trump are both spending a large amount of money on advertising in swing states.
Pennsylvania has been a particular point of focus for cash from each campaign due to its 19 electoral votes and Harris is reportedly spending around US$195 million ($284 million) in ad buys in the state, as compared to Trump's US$78 million ($113 million).
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Michigan and Georgia are then the second and third priorities for both Harris and Trump, with both candidates investing heavily in ad buys in those states.
Smith said the focus on swing states by presidential candidates can mean other areas of the country are comparatively ignored.
"This is another controversial thing about the electoral college, is that it means the election campaign is just fought in somewhere between five and 10 states.
"I was in Pennsylvania earlier this year, and just whenever you turn on the TV, it's just election ad after election ad, and 20 minutes down the road in New Jersey, you wouldn't have seen the same thing."
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