Mr. Biden was moving quickly to capitalize on his South Carolina victory and recast the Democratic primary campaign as a two-man contest between himself and Mr. Sanders.
Former Vice President Joseph R. Biden Jr. at Brown Chapel AME Church in Selma, Ala.
The Democratic presidential campaign took a dramatic turn on Sunday as a top candidate, former Mayor Pete Buttigieg, quit the race and started clearing the way for moderate voters to coalesce around candidates better positioned to stop Senator Bernie Sanders, the liberal front-runner for the party’s nomination.
Mr. Buttigieg made his decision after a devastating loss in Saturday’s primary in South Carolina, where a fellow moderate, former Vice President Joseph R. Biden Jr., won his first victory in the presidential race. The departure of Mr. Buttigieg could lift Mr. Biden’s political fortunes heading into the major Super Tuesday primaries, but might also benefit other candidates, particularly Senator Elizabeth Warren and former Mayor Michael R. Bloomberg, who also hold appeal with swaths of Mr. Buttigieg’s supporters.
Even before Mr. Buttigieg’s exit, Mr. Biden was moving quickly to capitalize on his victory and recast the Democratic campaign as a two-man contest between himself and Mr. Sanders. Yet there were also signs that Mr. Biden, Ms. Warren and other rivals were fighting for their own survival against Mr. Sanders on Super Tuesday, the single most important election date on the 2020 primary calendar.
In a show of strength, Mr. Sanders announced on Sunday morning that he raised $46.5 million in February, by far the biggest amount of any candidate so far, giving him a huge financial war chest. Mr. Sanders is using those funds to dramatically expand his advertising in states that vote deep into March, including Florida, Michigan and Ohio. Mr. Biden is not yet on the airwaves in those states or any other that votes past Tuesday.
The pressure to persevere on Super Tuesday was even more acute for other Democratic candidates as some reckoned with losses in the South Carolina primary on Saturday but were unwilling to quit a race that has been defined by unpredictability.
In a blunt memo on Sunday, Ms. Warren’s campaign all but admitted she no longer has a path to the nomination beyond a contested Democratic convention. Mr. Bloomberg appeared in a three-minute nationwide commercial on Sunday night, further pushing the bounds of what his billions could buy after his candidacy was undercut by his debate performances. And Senator Amy Klobuchar strained to make the case she was still a serious contender, boasting that she had been “in the top five vote getters in these small caucuses and primaries” in a local television interview.