Texas offered a different test. The state’s Democratic electorate is a mix of African-Americans and more conservative and affluent white voters who tend to back Mr. Biden, and younger, urban and Latino voters who tend to back Mr. Sanders. According to the exit polls, Mr. Sanders won Latinos by a margin of 50 percent to 24 percent across the Super Tuesday states, with a margin of 41 percent to 24 percent in Texas.
In an election night count that reflected the shift in the national political environment over the last week, Mr. Biden eventually overtook Mr. Sanders in the Texas returns, with a wide advantage among late-deciding voters who cast their ballots on Election Day. In a telling indication of how quickly moderate voters had coalesced behind Mr. Biden, the exit polls across the Super Tuesday states found that among voters who decided in just the last few days, Mr. Biden won by a margin of 48 percent to 21 percent.
In North Carolina, which separates out early and Election Day results, Mr. Biden won just 28 percent among early voters but 41 percent of the vote statewide after winning 52 percent among Election Day voters. Mr. Bloomberg saw his support collapse in the Election Day vote.
Mr. Sanders denied Mr. Biden a more sweeping victory with decisive wins of his own in the West, where Mr. Sanders can count on his strengths among Latinos, liberals and younger, urban voters without fully facing his weakness among African-American voters and conservative rural whites. The West also has the highest rate of early voting in the country, which helped blunt Mr. Biden’s surge.
Mr. Buttigieg and Ms. Klobuchar combined for 22 percent support in the exit poll in Colorado, where advance voters represented well over half of all voters — the largest share of the vote of any state on Tuesday. Their support was not recorded in the election night tabulation because they withdrew from the race, but they routinely breached 10 percent in early voting elsewhere in the country, including California.
The large early and absentee vote in some of the states most favorable to Mr. Sanders was enough to keep him close and competitive in the overall delegate count, despite 10 losses in 14 states. Over all, Mr. Biden holds only 45 percent of pledged delegates after Super Tuesday, according to preliminary Upshot estimates, while Mr. Sanders is expected to finish with around 39 percent. These tallies could change depending on the eventual result in California (which might not become official for weeks), but if they hold, Mr. Biden’s delegate lead would be far from irreversible. In fact, Mr. Sanders would need to defeat Mr. Biden by only three points in the remaining two-thirds of the country to overtake him.
A three-point deficit is not a daunting handicap, certainly not when Mr. Biden was polling 20 points lower just a few days ago. But the Super Tuesday results do not augur well for Mr. Sanders’s odds of pulling it off. He remained so competitive on Super Tuesday in part because of the large number of early and absentee voters who cast ballots before it became apparent that Mr. Biden was the viable moderate candidate.