It was not on matters of race alone that Mr. Biden found himself under biting attack. When Mr. Biden delivered a laudatory account of his own skills as a congressional negotiator, boasting that he had coaxed a tax increase out of the Senate majority leader, Mitch McConnell, the former vice president earned a swift rebuke from a fellow moderate, Senator Michael Bennet of Colorado.
“The deal that he talked about, with Mitch McConnell, was a complete victory for the Tea Party,” Mr. Bennet said, arguing that Mr. Biden had made foolish concessions to Republicans on government spending without getting much in return. “That was a great deal for Mitch McConnell. It was a terrible deal for America.”
And without condemning Mr. Biden by name, Senator Kirsten Gillibrand of New York, too, rejected his deal-making ethos and called attention to his history of taking more conservative positions on abortion rights — including his past support for a ban on federal funding for abortion, known as the Hyde Amendment. Mr. Biden only renounced his support for the measure earlier this month.
“When the door is closed, negotiations are made, there are conversations about women’s rights and compromises have been made on our backs,” Ms. Gillibrand said. “That’s how we got to Hyde. The how the Hyde Amendment was created — a compromise by leaders of both parties.”
If Mr. Biden spent much of the debate on defense, so at times did the ascendant left wing of the Democratic Party, as a group of moderates led by Mr. Biden raised doubts — and repeatedly expressed something verging on alarm — about Democrats’ embrace of the far-left ideas pioneered by Senator Bernie Sanders of Vermont.
Mr. Biden rejected Mr. Sanders’s demand for a single-payer health care system and said that seeking to expand coverage more incrementally was the more pragmatic approach. Two lesser known rivals, Mr. Bennet and former Gov. John Hickenlooper of Colorado, warned more ominously that Mr. Sanders and others who espouse his ideology could damage the Democratic Party and the country’s economy.
“If we don’t clearly define that we are not socialists,” Mr. Hickenlooper declared, “the Republicans are going to come at us every way they can and call us socialist.”