Ten percent of Democratic voters said they made their decisions on Tuesday, with another 19 percent deciding over the past few days. Twenty-seven percent said they made their decisions in the last month, while 42 percent made their minds up before then, according to the early data.
And early exit poll results show that those late-deciding voters broke decisively for former Vice President Joe Biden: 47 percent of those who decided in the last few days chose Biden, compared to 18 percent who chose Sen. Bernie Sanders, I-t., 12 percent who chose Sen. Elizabeth Warren of Massachusetts and 15 percent who chose former New York Mayor Mike Bloomberg.
Sanders led among those who decided earlier than that. Thirty-seven percent backed him, compared to 26 percent for Biden, 13 percent for Warren and 12 percent for Bloomberg.
Those results come on the heels of a flurry of activity in the nominating contest over the past several days.
Biden's commanding victory in Saturday's South Carolina primary prompted a flood of endorsements to come his way, two of them from former Democratic presidential hopefuls, Sen. Amy Klobuchar of Minnesota and former South Bend, Indiana, Mayor Pete Buttigieg.
Biden's campaign was hoping that late movement would be enough to blunt the rise of Sanders, who came into Tuesday as the delegate leader and hoped to expand on that lead with strong showings in California and Texas.
And Super Tuesday came with questions as to whether the big-spending Bloomberg would cut into Biden's vote share as they competed for moderate voters, considering the contests marked Bloomberg's first appearance on primary ballots.
The former New York City mayor peeled off about 19 percent of moderate voters, exit polls show. But Biden still held a significant lead among moderate and conservative voters, winning 41 percent of them compared to Sanders' 20 percent and Bloomberg's 18 percent in Super Tuesday states.
Results reported here reflect data combined from NBC News Exit Poll surveys in 12 of the 14 states holding Democratic primaries or caucuses on Super Tuesday (Alabama, California, Colorado, Maine, Massachusetts, Minnesota, North Carolina, Oklahoma, Tennessee, Texas, Vermont and Virginia). Results are weighted to reflect differences in the sizes of state electorates. The numbers will update as more exit poll data comes in.
The early round of exit polls show that nonwhite voters make up almost 40 percent of the electorate across the 12 states — white voters so far appear to be 61 percent of the electorate, while Hispanics make up 18 percent, black voters 14 percent and Asian voters 4 percent.
Biden's success in the early evening — the NBC News Decision Desk projected that Biden will win Virginia and North Carolina — came thanks in part to black voters. Biden won 62 percent of black voters in North Carolina, compared to Sanders' 17 percent. In Virginia, the margin was 69 percent to 17 percent for Biden and Sanders respectively.
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But there are early signs that Biden's overwhelming edge with black voters isn't translating to states outside the South. While Biden has a 48-point edge over Sanders with black voters in Southern states (Alabama, North Carolina, Oklahoma, Tennessee, Texas and Virginia), he has just an 11-point edge in other states voting on Super Tuesday.
Almost two-thirds of the Super Tuesday electorate, 63 percent, are 45 and older. Thirty-seven percent are ages 18 to 44.
While Sanders had a 15-point edge over Biden with first-time voters, those voters made up just 14 percent of the Super Tuesday electorate.
With 6 in 10 voters prioritizing a candidate who can beat President Trump over one who agrees with them on the issues, Biden led with those voters by 12 points. Conversely, Sanders had an 18-point lead with those who want a candidate who agrees with them on issues.
Liberal voters made up 61 percent of the electorate, with 25 percent of the total electorate identifying as very liberal and 36 percent identifying as somewhat liberal. Thirty-nine percent of the Super Tuesday electorate in the 12 states identify as moderate or conservative.
As Democratic voters decide whether to anoint Sanders, a democratic socialist, as their standard-bearer, Democratic voters in California, North Carolina, Tennessee and Texas all view socialism more favorably than unfavorably.
Health care remains the top issue for Democrats voting in the 12 states. Forty percent of Democratic Super Tuesday voters said health care was the most important issue to their vote, with climate change and income inequality at 22 percent and 21 percent, respectively, and race relations the top issue for 10 percent of the electorate.