Joe Biden v Donald Trump - four things that could decide who wins

Donald Trump and Joe Biden will do battle in November to determine who occupies the White House for the next four years.

This contest will be unique in modern history as a rematch between the current president and his immediate predecessor.

The contrast will be simple, according to Sean Spicer, who served as Mr Trump's first press secretary and worked for the Republican National Committee prior to that.

"For those people who say, well, during Trump, the policies of Donald Trump made my life better, more secure, made the economy and our communities better, it's a no brainer."

The Trump campaign will be hoping to distract from the weaknesses of their candidate - his legal troubles, his divisive rhetoric and his attempts to undermine the 2020 election results, which contributed to the January 2021 attack on the US Capitol.

But Mr Biden also has key vulnerabilities, struggling to sell his first-term achievements and trying to convince the public he has the energy for the campaign and a second term.

He paints his predecessor as out-of-control and a threat to America, and to democracy itself.

"Here, you've got somebody who's very well known, and you're just trying to prove he's a big risk." says Susan Estrich, a Democratic author and analyst who managed Michael Dukakis' presidential campaign in 1988.

It's a rematch few Americans say they want but it's a presidential choice that at this point they seem almost certain to get.

Here are four factors that will determine who comes out on top.

Mr Biden's approval ratings continue to languish in dangerous territory for an incumbent entering an election year. Public perceptions of Mr Trump are also negative, however.

By all indications, November's general election is going to be tight. National polls show the two candidates either neck and neck or Mr Trump with a slight advantage.

But this early in the race they are of limited usefulness, given the nature of the US political map. While Americans will head to the polls across the nation, this race will once again be decided in only a handful of states.

That's because the electoral college, the system the US has to pick its president, depends on candidates winning each state and most states are solidly Democratic or Republican.

The most crucial states that could go either way this year include Wisconsin, Pennsylvania and Michigan in the so-called Rust Belt, and Arizona and Georgia, two states that Mr Biden flipped Democratic in 2020.

Nevada is also considered a toss-up but its small population makes it a less valuable prize.

A few states that have been battlegrounds in previous election cycles have slipped off this map - Florida and North Carolina have trended Republican of late, while Virginia and Colorado appear to be more solidly Democratic.

So while national polls provide fodder for political commentators, a much smaller subset of voters will ultimately be the ones who matter.

Polling showing Mr Trump inching ahead in these key states have caused alarm among some Democrats, but the size of his lead is not statistically significant.

When it comes down to it, Americans tend to vote from their wallets in national elections - for the governing party in good times and the opposition in bad.

"It's the economy, stupid" was the mantra of Bill Clinton's successful 1992 presidential campaign, and the refrain has become political gospel in the decades since.

One of the factors that makes 2024 challenging to predict is that, on the whole, economic indicators are positive.

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And if you're anywhere else, Republicans have won control of both chambers of Congress, yielding Trump limited congressional oversight for at least 2 years.