Super Tuesday is the biggest day of voting in the US outside of the November election.
But what is it, what makes it super – and what will be different about this year?
What is Super Tuesday?
Super Tuesday is the day when the most US states choose who they think should be their candidates for president.
In sixteen states across the country, Democrats and Republicans will say who they want to see on the ballot come November.
Super Tuesday – an unofficial name that has been used since at least 1976 – is also when the highest number of delegates will be awarded to candidates.
Although voters cast ballots for their preferred presidential candidates, it is the delegates to the national party conventions who ultimately select the presidential nominees for each major party.
That means candidates need to secure delegates, largely by winning in the primaries, to guarantee their path to the election.
More than a third of the total delegates available will be allotted on Super Tuesday.
In the Republican contest, 874 of 2,429 delegates will be up for grabs, while the Democrats will award 1,420 delegates.
When is Super Tuesday?
Super Tuesday is on 5 March this year.
Read more from Sky News:
Nikki Haley becomes first woman in history to win Republican primary
Trump’s dominance grows after he wins three more state caucuses
Please use Chrome browser for a more accessible video player
What is Super Tuesday? US correspondent Mark Stone explains
What is different about this Super Tuesday?
Super Tuesday is normally the moment “when candidates are whittled down from a pack to just a few”, US correspondent Mark Stone explains.
“This year, it’s not so super.”
That’s because the race is already dominated by clear front-runners in each party.
President Joe Biden is the presumptive Democratic candidate, and it is highly unlikely anything will change that.
And Donald Trump has emerged as the firm favourite for the Republican Party.
But there are still a few “key moments to watch”, Stone says.
“Nikki Haley is Trump’s competition, she’s well behind in most polls and even lost her home state – but she is fighting on.
“If she pulls out, then this Super Tuesday will mark the unofficial crowning moment for Trump as the Republican candidate.
“Tuesday will be the moment to judge just how strong Donald Trump is and how electable he is in November.”