(CNN) Joe Biden surged to victory in South Carolina's Democratic presidential primary with a base rooted in black voters, those over the age of 65 and moderates.

The former vice president won around 3 in 5 black voters, dominating over his closest competitor, Vermont Sen. Bernie Sanders , according to results from CNN's exit poll Saturday. The demographics of South Carolina 's Democratic primary voters stand apart from the race's first three states, marking the first state with a majority black electorate to weigh in on the Democratic nomination fight.

Sanders received the backing of almost 1 in 5 black voters. Businessman Tom Steyer -- who exited the race later Saturday night -- came close to Sanders, winning around 1 in 7 black voters.

While Biden won big among black voters over the age of 60, with about three quarters of those voters supporting him, he and the Vermont senator ran about even among black voters under 30. Sanders had 38% while Biden had 36%.

The racial composition of South Carolina's Democratic primary electorate has shifted slightly compared with 2016, and exit polls indicate it is slightly less black and a bit more white than it was four years ago.

That is most likely due to the state's open primary structure. Any registered voter could participate in the Democratic primary, and -- with the Republican primary canceled -- some independents and Republicans, who are more likely to be white, may have chosen to participate in the Democratic contest. Around a quarter of Democratic voters on Saturday identified as independents, according to polling -- up significantly from 2016 when 16% said so. Four years ago, 82% of the electorate said they were Democrats, this year, it is closer to 7 in 10.

Around two-thirds of voters over the age of 65 supported Biden in his run in South Carolina, no other candidate even hit 15% among this group.

Biden also led among moderate voters with a little more than half of the group supporting him. The state's electorate includes more voters who describe themselves as moderate or conservative than any of the other three states to vote. About half call themselves moderate or conservative, compared with about a third in Iowa and Nevada and roughly 4 in 10 in New Hampshire

Former South Bend, Indiana, Mayor Pete Buttigieg and Minnesota Sen. Amy Klobuchar , who also claim the moderate lane in the Democratic primary race, won the backing of fewer moderates than Biden, with Buttigieg at around 1 in 10 in the group and Klobuchar in the single digits.

The former vice president, though, also won over voters who consider themselves very liberal, with around 2 in 5 of the group, surpassing Sanders with 3 in 10. Massachusetts Sen. Elizabeth Warren followed Sanders with around 1 in 7 very liberal voters.

Biden tops field in favorability

Biden dominated in favorability Saturday, according to polls, landing the highest rating of any candidate tested.

Around three-quarters of voters in polling said they have a favorable opinion of him. Biden's ratings were significantly higher among black voters, with 84% holding a favorable opinion.

Steyer, Sanders and Warren all hit slightly above half in their favorability numbers, with about 2 in 5 voters finding each unfavorable. Buttigieg landed at around half favorable, with less than half unfavorable. And Klobuchar's unfavorability barely outpaced her favorability in polling.

Only a quarter of voters said they have a favorable opinion of former New York City Mayor Mike Bloomberg , while two thirds found him unfavorable.

Late deciders and the Clyburn endorsement

About a third of South Carolina voters said they made up their minds about whom to support in the final days of the campaign there, according to exit poll results from CNN. That's significantly lower than the half who decided late in New Hampshire, and higher than the 1 in 10 who did so in Nevada, but about on par with late deciders in Iowa.

The survey suggests white voters in South Carolina were more apt to make up their minds in the last few days than were the state's black voters. Women were also more apt to make their final decision in the last few days than were men.

Roughly 1 in 5 overall said they made up their minds earlier in February, and about twice as many said they had decided whom to support before February, when the first voting of the primary season began.

South Carolina Democratic Rep. James Clyburn's late endorsement of Biden was a critical factor for about a quarter of South Carolina's Democratic primary voters, while a similar share said his announcement of support for the former vice president did not matter to their vote at all. Among black voters, the share calling it the most important factor in their vote rises to about a third.

Nearly 1 in 5 voters on Saturday were participating in their first Democratic primary, that appears to be slightly higher than the share who said so in New Hampshire (13%).

Electability and unity

Exit polls suggested South Carolina Democratic primary voters were more apt than those in the race's first three states to say they want the party to nominate a candidate who agrees with them on the issues.

About 4 in 10 said they'd rather see a nominee who agrees with them on the issues, while a small majority said they want the party to nominate someone who can beat President Donald Trump . In each of the other states where caucuses or primaries were held, more than 6 in 10 said they preferred a nominee who could win.

In South Carolina, ideology appears to work in the opposite way than it has in some other states on this question: Those who consider themselves moderate or conservative are almost evenly split on this question, while liberals are more apt to say they want a winner. In both Iowa and Nevada, the pattern was reversed, with moderates and conservatives more apt to say they wanted a winner than were liberals. In New Hampshire, voters preferred someone who could beat Trump across ideological lines, though moderates were slightly less likely to say so.

South Carolina's Democratic primary voters were also less likely than those in New Hampshire to say they're angry about Trump's administration. About 8 in 10 said they were angry in New Hampshire, that number dips to roughly half in South Carolina.

Still, according to the polling, voters are largely on board to vote for the Democratic nominee in November regardless of who it is. Only about 1 in 6 said they were not committed to voting for the Democrat in November.

About 4 in 10 said they're seeking a candidate who can bring needed change, while just more than a quarter each said they want one who cares about people like them and one who can unite the country.

On the issues

Health care remains the most important issue for Democratic primary voters, according to the exit poll results.

Overall, about 4 in 10 in polling Saturday said that it was the most important issue in their vote. About half as many said that income inequality was the key factor in their vote, and roughly 1 in 6 said race relations was a critical issue. Slightly fewer chose climate change as their top concern.

Although about the same share of black and white voters in South Carolina call health care the top issue in their vote, there's a gap by race on climate change and race relations. Among white voters, climate change lands second, with nearly a quarter calling it their top issue. Among black voters, about a quarter each choose race relations and income inequality as their top issue, while the share choosing climate change stands in the single digits. One in 10 white voters names race relations as their top concern.

South Carolina's votershave expressed lower support for a plan like "Medicare for All" than voters in the earlier contests. About half said they support replacing all private health insurance with a single government plan for everyone. In Iowa, New Hampshire and Nevada, about 6 in 10 supported it.

About half of those who came out to vote Saturday said the nation's economic system is in need of a complete overhaul. Just 1 in 10 said the economic system works well enough as it is.

Nearly 6 in 10 women said they think the economic system needs a complete overhaul, compared with 4 in 10 men. Black voters were nearly 20 points more likely than whites to say that the system needs one.

The South Carolina electorate is also more religiously active than Democratic primary voters in New Hampshire, the only other state thus far where exit polls measured religious behavior. About 4 in 10 said they attend religious services at least once a week; that stood at just 13% in New Hampshire. The finding is connected to the racial diversity of the electorate, but not entirely driven by it: a majority of black Democratic primary voters in South Carolina said they attend services weekly, compared with about 3 in 10 white voters.

The CNN Exit Poll was conducted by Edison Research for the National Election Pool. Results are based on interviews conducted throughout the day with 2,178 randomly selected Democratic primary voters at 35 precincts in South Carolina. Results for the full sample have a margin of error of plus or minus 4 percentage points.

This story has been updated with the latest exit poll figures from the South Carolina primary.