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WASHINGTON — Former Vice President Joe Biden and Sen. Bernie Sanders, I-Vt., are locked in a tight contest in South Carolina, according to a new NBC News/Marist poll ahead of the state's Democratic primary Saturday.

Biden gets the support of 27 percent of likely Democratic primary voters in South Carolina, while Sanders gets 23 percent — well within the poll's margin of error of plus-minus 6 percentage points.

They're followed by billionaire activist Tom Steyer at 15 percent, former South Bend, Indiana, Mayor Pete Buttigieg at 9 percent, Sen. Elizabeth Warren, D-Mass., at 8 percent and Sen. Amy Klobuchar, D-Minn., at 5 percent.

No other candidate gets more than 3 percent in the poll.

The survey was conducted Feb. 18 to Feb. 21 — before the results were known from Saturday's Nevada caucuses, which Sanders easily won, beating Biden by more than 2 to 1.

Steyer's double-digit showing comes as he's spent about $20 million on TV and radio ads in the state, according to ad spending data from Advertising Analytics, which is nearly 10 times more than the second-biggest advertiser, Buttigieg.

"South Carolina closes the chapter on the first phase of the presidential sweepstakes," said Lee Miringoff, director of the Marist College Institute for Public Opinion, which conducted the poll for NBC News.

"Will Biden come off the canvas? Will Sanders continue his charge to Super Tuesday? Will someone else emerge as a top-tier candidate?"

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In the new NBC News/Marist poll, Biden performs best among likely voters who are moderates (getting support from 38 percent of them), African American (35 percent) and 45 or older (34 percent).

Sanders does best among those younger than 45 (40 percent) and self-described progressives (34 percent).

And while Sanders trails Biden among African American likely voters, the margin is closer than it was four years ago — Biden gets 35 percent, Sanders gets 20 percent and Steyer is at 19 percent.

In 2016, by comparison, Hillary Clinton crushed Sanders among African American voters, 86 percent to 14 percent, according to the exit poll.

Clinton won the state by nearly 50 points in the primary four years ago.

Buttigieg, meanwhile, struggles with African American voters, getting support from just 4 percent of them, versus 17 percent among white South Carolina Democratic primary voters.

Also in the poll, 72 percent of Sanders backers say they strongly support him, versus 61 percent of Biden's supporters and 60 percent of for Steyer's.

And 47 percent of likely South Carolina Democratic primary voters say a candidate who comes closest to them on the issues is their most important consideration. Sanders wins 29 percent of those voters, while Biden gets 18 percent and Steyer gets 14 percent.

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By contrast, 44 percent say the candidate who has the best chance to defeat President Donald Trump is most important to them. Biden gets 35 percent of those voters, while Sanders gets 17 percent.

GOP still holds the advantage in South Carolina

Turning to the general election in November, 53 percent of all registered voters in the state approve of Trump's job, while 41 percent disapprove.

Republicans also enjoy a double-digit advantage in congressional preference in the GOP-leaning state, with 53 percent of all voters saying they prefer a Republican-controlled Congress, while 35 percent want Democrats in charge.

And in a hypothetical Senate matchup for November, Republican Sen. Lindsey Graham leads likely Democratic challenger Jamie Harrison by 17 points among registered voters, 54 percent to 37 percent.

The NBC News/Marist poll of South Carolina was conducted Feb. 18-21 of 2,382 registered voters and has a margin of error of plus-minus 2.6 percentage points.

The margin of error for the 539 likely Democratic primary voters is plus-minus 6.0 percentage points.