Today is one of the most important milestones in the race to see who will challenge Donald Trump to become the next president of the United States.
Bernie Sanders goes into so-called Super Tuesday as the surprise leader in the race to be the Democratic Party nominee, but after a win in the South Carolina primary former Vice President Joe Biden is hot on his heels.
And he has had a further boost with the support of three ex candidates, Amy Klobuchar, Pete Buttigieg and Beto O’Rourke, who have all backed Mr Biden to be the Democratic party candidate for president.
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So what is Super Tuesday and why is it important?
It’s important for three reasons – it is when the most US states hold contests to pick a presidential nominee, where the most people get to cast their ballot and where the highest number of delegates will be allotted to candidates.
More than a third (34%) of all delegates for the Democratic National Convention are up for grabs. On Super Tuesday 1,357 delegates will be awarded. You need 1,991 to get the nomination.
Which states are voting?
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Fourteen states and one US territory are voting. They are all over the country – from Maine to California. Traditionally Republican states like Oklahoma and Texas are in the mix, so are states more in the middle, like Virginia, North Carolina and Colorado and reliably Democratic states like Massachusetts too.
Each state is given a certain number of delegates based on a combination of population and significance in the Democratic Party. No one will get the nomination based on what they get on Super Tuesday alone, but it can give you a massive boost.
Why does it matter so much this year?
The race has had a very crowded field – with a sprawling battle between moderate and progressive candidates. But with Biden’s sudden surge in South Carolina (driven by large support from African Americans of all ages), Pete Buttigieg, Amy Klobuchar and Tom Steyer quit. It appears to be an attempt to unite and fend off the Bernie wave before it’s too late.
The race now seems a clear cut battle between Sanders and Biden. The former vice president will be hoping he can hoover up much needed votes from his rivals, turned endorsers.
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What to look out for?
Can Joe Biden build on the momentum he’s generated? Will Klobuchar and Buttigieg’s supporters flock to him. If so, he’s in with a chance. But it still won’t be easy. And, was his success with black voters in South Carolina a one-off or part of something bigger. He claims his popularity among African Americans will get him to the White House.
Will the Sanders runaway train slow down? He’s the front runner nationally, with a powerful and loyal populist movement behind him. He’s been particularly focused on delegate-heavy California where he’s polling very well and that strategy could pay off. But establishment Democrats are still nervous about him and if he comes third in a number of states, it will be harder for him to convince people he’s the one who can beat Trump.
The Michael Bloomberg factor: The former New York mayor decided to skip the early states and put all his energy into Super Tuesday. He’s ploughed $500m (£392m) into TV advertising and things were looking up for him early on. But after some poor TV debate performances, he’s got a very big hill to climb to scramble into contention.