Charleston, South Carolina (CNN) Joe Biden needs a win Saturday night. And if he, as recent polling suggests, pulls it off, how big that victory is could determine the course of the Democratic nomination fight as it heads into Super Tuesday on March 3.

The week leading into South Carolina's primary has been one of the best of Biden's campaign, with a strong debate performance , a key endorsement and rising polls in the state providing him with needed momentum at a critical time.

Vermont Sen. Bernie Sanders came into South Carolina with more momentum than any other candidate, so how much he is able to close the gap with Biden will be key to how his performance is viewed.

And if Sanders is able to keep it close, it may be because of billionaire Tom Steyer , who has staked his campaign on South Carolina and is hoping to win over a significant portion of black voters, potentially undercutting Biden's lead in the state.

For all the other candidates, like former South Bend, Indiana Mayor Pete Buttigieg , Minnesota Sen. Amy Klobuchar and Massachusetts Sen. Elizabeth Warren , South Carolina serves as a stopover on the way to Super Tuesday. None of those candidates expect to finish in the top two on Saturday and are already looking ahead to the next contests.

Can Biden get the big bounce he needs?

Biden takes selfies with people in the crowd after a South Carolina campaign launch party on February 11, 2020 in Columbia, South Carolina.

Now is the time for the former vice president to deliver what he has promised for weeks: A first place finish in South Carolina.

Before any 2020 votes had been cast, he called South Carolina his "firewall" -- the one must-win in the four early states. His losses in Iowa, New Hampshire and Nevada have drastically increased pressure here to get a big win, and a bounce nationally in the three days leading into Super Tuesday, when 14 states and American Samoa, representing 34% of all Democratic pledged delegates, cast their votes.

Biden's base is African American voters, and those voters make up the majority of the Democratic electorate in South Carolina. As long as he maintains a clear majority of support from those voters, he should also be able to rack up delegates on Super Tuesday in other Southern states with largely black primary electorates: Alabama, Arkansas, North Carolina and Tennessee.

If Biden wins big, he and his allies are likely to immediately pressure other moderates in the race to step aside so that voters and donors can coalesce around a single alternative to Sanders.

But if Sanders can keep it close, it could rob Biden of that bounce he desperately needs to generate momentum heading into Super Tuesday.

A win Saturday would be the first time, in three presidential runs spread across 32 years, Biden has ever won a state. A loss would effectively mark the end of his chances at winning the Democratic delegate race.

Can Bernie Sanders keep it close?

Sanders and his wife Jane Sanders arrive for a campaign rally at Vic Mathias Shores Park on February 23, 2020 in Austin, Texas. With early voting underway in Texas, Sanders is holding four rallies in the delegate-rich state this weekend before traveling on to South Carolina. Texas holds their primary on Super Tuesday March 3rd, along with over a dozen other states.

Sanders came to South Carolina on a roll after overwhelming the field in Nevada. Polls showed him closing in on Biden, who has led here for the entire campaign.

But as the days passed, his momentum seemed to slow. Biden enters primary day as the clear the favorite. The question now: Can Sanders keep it close?

South Carolina was the beginning of the end of Sanders' 2016 campaign. He lost to Hillary Clinton by more than 47 percentage points, the first in a series of drubbings across the South.

But Sanders' standing with African-American voters has improved over the years and he continues to lap the field with younger voters across racial lines.

The Vermont senator could charge into Super Tuesday with a strong second place finish here. But if Biden were to win by 20 percentage points or more, it would raise red flags for Sanders' campaign going forward.

What role does Tom Steyer play?

CNN Democratic Presidential Town Hall with Businessman Tom Steyer Moderated by CNN's Dana Bash St. Anselm Manchester, New Hampshire February 2020

Steyer has gone all-in on South Carolina.

The billionaire businessman has spent more than $22 million on television and radio ads here and blanketed the state with more events than any candidate in this race, hoping that a direct and persistent outreach to black voters could cut into Biden's strength with the powerful voting bloc.

And, if polling is to be believed, the strategy has worked. A recent Monmouth University poll found Steyer at 15% in the state, neck-and-neck with Sanders, the race's frontrunner.

Biden still looks strong in the state, but if Sanders is able to keep it close with Biden on Saturday, it may be because Steyer cut into the former vice president's lead with black voters.

One key question remains for Steyer, though: Where does he go from here?

Steyer has spent more than $35 million on ads in California, and nearly $3 million in Texas, but even with a strong showing in South Carolina, it's hard to see where Steyer continues racking up delegates.

The other contenders

There are five other Democrats in the race -- though none appear to have a realistic shot at finishing at or near the top in South Carolina.

Former New York Mayor Michael Bloomberg isn't on the ballot. What he might hope for most is muddy results that would deprive Biden of a bounce.

Buttigieg and Klobuchar are both struggling in South Carolina. They've failed to make real inroads with African American voters -- and if that doesn't change immediately, it would all but eliminate their paths to the nomination.

Warren hasn't yet finished higher than third place -- and that isn't likely to change in South Carolina. But if she can turn in a stronger-than-expected performance that shows her ability to perform across Democrats' diverse base, it could help her on Super Tuesday, where she's polling ahead of Buttigieg and Klobuchar in California and Texas and needs to beat Sanders in her home state.

Then there's Hawaii Rep. Tulsi Gabbard, who hasn't yet dropped out despite showing no indication she can get out of the low single digits anywhere.