Washington (CNN) Joe Biden holds a wide lead in South Carolina, while the former vice president, Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren are knotted up in Nevada, according to new CNN polls conducted by SSRS in the third and fourth states to cast ballots for the 2020 Democratic nomination .

Biden tops Warren by 21 points in South Carolina -- 37% of likely voters back the former vice president, 16% Warren and 11% Sanders. In Nevada, there is no clear leader, with Biden and Sanders tied at 22% of likely caucusgoers with 18% for Warren, all within the poll's margin of sampling error. In neither state does any other candidate reach double-digits.

Biden's strong standing in South Carolina rests on support from black voters. Overall, 45% of black likely primary voters back Biden, more than 30 points ahead of his closest competitor. Among white likely primary voters, however, Biden and Warren are deadlocked: 29% favor Biden, 28% Warren.

Nevada's three-way race rests on the demographic and political divides that are driving the contest nationwide. Liberal likely caucusgoers break heavily for Sanders, while moderate and conservative caucusgoers give Biden a wide edge. Those under age 50 break toward Sanders: 35% for him vs. 13% for Warren and 12% for Biden. Among those over 50, 32% back Biden, 23% Warren and 11% Sanders. Voters with college degrees are more in Warren's corner, while those without degrees split between Sanders and Biden with Warren lagging behind.

There is room in both states for these numbers to move. So far, 44% of likely caucusgoers in Nevada and 45% of likely voters in South Carolina say they've chosen a candidate and made up their mind. Another 38% in each state say they have a preference but could change their mind and 18% in Nevada and 17% in South Carolina don't have a preference yet.

Biden stands alone in South Carolina when likely voters are asked to rate their level of enthusiasm. Nearly half, 48%, would be enthusiastic about a Biden nomination, outpacing Warren's 35%, Sanders' and California Sen. Kamala Harris's 23% and South Bend, Indiana, Mayor Pete Buttigieg's 19%. In Nevada, more than 4 in 10 say they would be enthusiastic about each of the top three -- 47% for Sanders, 44% for Biden and 42% for Warren -- while 22% each would be enthusiastic about a Harris or Buttigieg nomination.

In both states, however, majorities would at least be satisfied with any of these five candidates. The share saying they would be dissatisfied or upset with any of these five peaks at 37% for Buttigieg in South Carolina and 28% for Harris or Buttigieg in Nevada.

On the issues and electability

About six in 10 likely Democratic voters or caucusgoers say it's more important to nominate a candidate with a strong chance of beating President Donald Trump than it is to nominate one who shares their views on the issues. And in both states, the group that is focused on beating Trump is more apt to favor Biden over Sanders. In Nevada, they are also more apt to favor Warren than are those focused on issues, her numbers are about the same across those groups in South Carolina.

Regardless of how they rate the importance of a candidate's positions on the issues, Nevada and South Carolina Democrats seem to differ over who can best handle the top issues facing the field. On health care, South Carolina's likely voters favor Biden -- 34% say he'd do the best job on it vs. 17% for Sanders and 16% for Warren -- while those in Nevada give Sanders an edge -- 32% say the Vermonter would do the best job on health care, 25% Biden, 17% Warren.

In Nevada, there's a massive divide within likely caucusgoers over health care along ideological lines, mirroring the debate the candidates have had publicly over the merits of "Medicare for All." Fully 50% of liberal likely caucusgoers say they trust Sanders most on health care with 20% naming Warren and 15% Biden, while Sanders trails Biden by 11 points among moderate and conservative likely caucusgoers (31% Biden, 20% Sanders and 14% Warren). The ideological gap is narrower in South Carolina.

Biden holds a wide edge overall on each of the five issues tested in South Carolina (health care, the climate crisis, gun policy, the economy and immigration. In Nevada, however, things get tighter outside of health care. On no other issue does a single candidate earn the trust of even 25% of likely caucusgoers, with Sanders, Biden and Warren clustered near the top across all five.

Rating Trump

Looking beyond the primaries, the President's approval rating in Nevada -- likely to be a critical battleground state in 2020 -- is underwater, 51% disapprove while 41% approve. That's about the same as it was last October just before Democrats won a Senate seat there, one of two picked up from Republicans in the 2018 midterms. In South Carolina, Trump's ratings outpace his national marks, which currently hover around 40% approval, with 49% approving and 47% disapproving. In both states, there is a 90-point gap between where Republicans and Democrats stand on Trump's approval, with independents tilting negative.

The surveys were conducted from September 22 through 26, during which time House Democrats announced a formal impeachment inquiry into the President . Looking at interviews conducted before and after the announcement of the inquiry, there does not appear to be a shift in Trump's ratings.

The Republican Party in both states has canceled its Republican nominating contest for 2020. Republicans and Republican-leaning independents largely back their party's decision, though. In South Carolina, 62% approve of canceling the primary, while 52% approve of the Nevada GOP's cancellation of its caucus. But even among those Republicans and Republican-leaners who disapprove of the decision to cancel the primary or caucus, the President is still deeply popular (83% approve of his job performance in Nevada, 74% in South Carolina).

The CNN polls in Nevada and South Carolina were conducted by telephone among random samples of adults in each state. In Nevada, results among the 1,203 adults have a margin of sampling error of plus or minus 3.6 percentage points, it is 7.1 points for results among the 324 likely Democratic caucusgoers. In South Carolina, results among 1,200 adults carry an error margin of 3.4 percentage points, while those among the 406 likely Democratic primary voters have an error margin of 5.9 points.