Biden vs Warren?….Others say wait a minute…..

For months, the Democratic presidential race has seemed to move inexorably toward a confrontation between former Vice President Joseph R. Biden Jr. and Senator Elizabeth Warren of Massachusetts. As Ms. Warren gathered financial support and strength in the polls, Mr. Biden steadily slid on both fronts while the rest of the Democratic field stagnated with voters. A jumbled primary appeared on the verge of becoming a contest between two front-runners.

But the debate in central Ohio on Tuesday night showed that the rest of the Democratic pack was not ready to yield.

From the moderate wing of the party, Mayor Pete Buttigieg of South Bend, Ind., and Senator Amy Klobuchar of Minnesota are now confronting Ms. Warren directly on her policy views and challenging Mr. Biden implicitly for his status as the party’s dominant centrist. From the left, Senator Bernie Sanders of Vermont has returned to the race with force after a heart attack that shook his candidacy, collecting valuable endorsements from prominent left-wing women in Congress, including Representative Alexandria Ocasio-Cortez of New York.

Mr. Buttigieg and Ms. Klobuchar, in assailing Ms. Warren by name, and Mr. Sanders, in rolling out endorsements from the most coveted figures in progressive politics, are acknowledging the same urgency about halting the drift toward a two-person primary.