Former US Vice President Joe Biden holds an interesting and unenviable record. He’s run for President of the United States three times – 1988, 2008, and now in 2020. And in those three campaigns, he has never won a single primary. Not one, not ever.

Since entering the present contest as the frontrunner, he’s had a thoroughly miserable time of it. His campaign has been marred by Biden’s trademark flubs and gaffes in front of the camera, and his old-style moderate Democrat act has largely failed to capture the attention of a liberal primary electorate that seems more interested in a candidate who can scream and shout about the badness of President Trump than in someone with Biden’s more moderate appeal.

In the first three contests, Biden has had a horrible run of results. He barely featured in Iowa and New Hampshire, and in Nevada, where his support from the big trade unions was supposed to deliver a victory, he finished a very distant second.

But South Carolina is a very different place, and the signs seem to point to a big Biden bounceback in tomorrow’s key primary.

For one thing, South Carolina is the first contest to take place in the former “deep south” – a place where the Democratic electorate skews heavily toward older and black voters, which is the one slice of the electorate Biden has been doing well with.

For another, since his early triumphs, Sanders has been under a sustained assault on the basis of his electability, with Democrats openly wondering whether a Sanders nomination would cost them their majority in the House of Representatives, as well as handing President Trump a second term.

The most recent polling in the state gives Biden a commanding – and surprising lead.

All of this is critical because the South Carolina vote comes just before the most decisive day in the primary – Super Tuesday, just three days later. Biden’s campaign is out of money, and out of momentum. Sanders could put an end to the fight, in practice if not in name, with big wins in California (which seems certain) and Texas (which seems possible) on Tuesday next. If the Democrat moderates want to stop him, they need to find a candidate to unite behind, and quickly.

All of this makes tomorrow’s election in little South Carolina absolutely critical. A big win for Joe Biden will probably mean three days of great media coverage and momentum heading into Super Tuesday. A narrow win, or a loss to Sanders, and the contest may well be over.

The fascinating thing about South Carolina, though, is that the Democrats are having what is known as “an open primary”. This means that voting in it is not restricted to Democrats, but is open to Republicans and non-aligned voters already. Some Trump supporters in the state are openly encouraging republican voters to cast ballots in the election for Bernie Sanders – on the theory that he’ll be much easier for their man to beat in November.

Imagine the mess that will unfold if Sanders wins South Carolina – and likely the nomination – tomorrow with the help of Trump voters. It’ll make Russiagate look like a minor squabble.