Former vice president Joe Biden picked up some big-name endorsements — including those of two former Democratic rivals, Sen. Amy Klobuchar (Minn.) and former South Bend, Ind., mayor Pete Buttigieg — a day ahead of Super Tuesday, when 14 states will cast their votes.

Harry M. Reid (D-Nev.), the former Senate majority leader, and Beto O’Rourke, the former Texas congressman, also endorsed Biden on Monday.

A consolidation of the party’s moderate wing came as fears grow that Sen. Bernie Sanders (I-Vt.), a self-described democratic socialist, could amass an insurmountable lead in delegates. A third of the pledged delegates for the party’s presidential nomination are up for grabs on Tuesday.

With a decisive win in Saturday’s South Carolina primary and his spate of new endorsements, Biden is seeking to turn the nominating contest into a two-person race against Sanders. The Vermont senator is leading polls in delegate-rich California and Texas and is aiming to build a formidable lead ahead of the Democratic National Convention.

Former New York mayor Mike Bloomberg will appear on ballots Tuesday for the first time, facing the first real test of his candidacy after spending half a billion dollars on his campaign. Sen. Elizabeth Warren (D-Mass.) and Rep. Tulsi Gabbard (D-Hawaii) also are competing in the Super Tuesday contests. Investor Tom Steyer dropped out of the race over the weekend after disappointing showings in South Carolina.

More on the election: