Former vice president Joe Biden has to win the South Carolina primary on February 29 or else it's game over for the erstwhile frontrunner. Polls since late 2019 installed Biden as the Democratic Party's presidential nominee favorite until Sen. Bernie Sanders (I-VT) came along with a string of two straight victories in New Hampshire and Nevada.

South Carolina, whose population is 27% African-American, has long been seen as a Biden stronghold. Biden is still favored to win the Palmetto State, however. But whereas before there was this aura of inevitability about a Biden win, now there's anxiety the state might slip away from Biden at the last moment.

A new CBS News-YouGov poll shows Biden the favorite presidential candidate among 28% of voting Democrats and Independents in South Carolina compared to Sanders' 23%. Biden's lead over Sanders and everyone else still in the running was once 30% in South Carolina.

Billionaire Tom Steyer came in third, with 18% of respondents saying they favored him as the nominee. The poll showed 12% of respondents in favor of Sen. Elizabeth Warren (D-MA), while 10% said they'd vote for former South Bend, Indiana Mayor Pete Buttigieg. Only 4% of voters said they supported Sen. Amy Klobuchar (D-MN).

Former New York City mayor Michael Bloomberg (D) isn't competing in South Carolina, but is instead focusing his campaign on the 14 Super Tuesday states. Super Tuesday, when a third of all delegates will be awarded, takes place March 3.

Biden is confident he'll do well on Super Tuesday since many of these states have racially diverse voting populations. Biden enjoys strong support among minorities but is having to win that support back on account of his poor showing in Iowa, New Hampshire and Nevada that dented his aura of inevitability.

Biden also polls favorably among whites that comprise 67% of the South Carolina's population. Biden has always polled well among blacks and Latinos but Sanders' win in the recent Nevada caucus saw him sweep the Latino vote. 

Sanders won Nevada with 46.8% of the vote to Biden's 20.2%. Political pundits said Sanders' win can be put down to expert organizing, a well-funded media campaign and big-spending while other Democrats cut down on spending. Sanders has also been on the ground in Nevada the longest compared to his rivals thanks to his strong grassroots organization.

Biden, it seems, will have to emulate Sanders' keys to victory, and then some, as the CBS News-YouGov poll shows him with a thin 5% lead over Sanders.