DES MOINES, Iowa — The leading Democratic presidential candidates clashed on Tuesday over America’s role in the Middle East and their credentials to be commander in chief, as the progressive candidates highlighted their dovish credentials and the moderates called for pragmatism in the last debate before the high-stakes Iowa caucuses next month.
The six candidates also debated the fraught subject of whether a woman could win the presidency, an issue that had produced a breach in recent days between the two top liberal candidates, Sens. Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts.
Meeting onstage for the first time since President ordered the killing of Gen. Qassem Soleimani of Iran this month, and in a state known for its anti-interventionist tendencies, each of the six contenders urged restraint about projecting American power.
Mr. Sanders said he and Mr. Biden listened to the same arguments by President George W. Bush and top officials in his administration at the time “and I thought they were lying” and voted against the authorization.
Mr. Biden, a former chairman of the Senate Foreign Relations Committee who touts his security credentials, voted in favor of the authorization in 2002.
“It was a mistake to trust that they weren’t going to go to war,” Mr. Biden said. “They said they were just going to get inspectors in. The world, in fact, voted to send inspectors in, and they still went to war.”
But Mr. Biden said that as President Barack Obama’s vice president, he worked to bring troops back home. “It was a mistaken vote, but I think my record overall on everything we have done, I’m prepared to compare it to anybody’s on this stage,” he said.
The debate was the seventh in the race to find a November election challenger to President Trump.
It came as opinion polls in recent days have shown a tight race among four candidates — Mr. Biden, Mr. Sanders, Sen. Elizabeth Warren, and Pete Buttigieg, former mayor of South Bend, Ind.
Joining the four in the debate were U.S. Senator Amy Klobuchar and billionaire activist Tom Steyer.
The debate stage was the least crowded since the debates began in June, with the Democratic National Committee’s toughened polling and fund-raising requirements to qualify eliminating other candidates.
Tension has been brewing lately between Mr. Sanders and Ms. Warren, fellow progressives who until now have largely avoided criticizing each other.
Ms. Warren chastised Mr. Sanders over the weekend following a report that his campaign instructed volunteers to speak poorly of her to win over undecided voters. The tensions escalated on Monday after CNN reported Mr. Sanders told Ms. Warren in a private 2018 meeting that he didn’t think a woman could win the election, a charge that Mr. Sanders vigorously denied but that Ms. Warren said was true.
With two surveys showing Pete Buttigieg losing support in Iowa, the former mayor is in need of a breakout to regain strength before the caucuses.
Those shifting dynamics meant Tuesday’s debate was unlike any of the others that came before it this cycle. The generally polite disputes over policy items including health care and immigration were replaced by increasingly bitter and personal knocks, experts said.
“The debates are always important — but this one’s probably the most important for these candidates,” said Scott Brennan, a former Iowa Democratic Party chair and current committeeman. “We’ve got at least four people who are bunched right there together at the top. So how do you break out?”
The debate, on the campus of Drake University and televised on CNN, marked the first forum with an all-white lineup.
Mr. Sanders is eager to take the fight to Mr. Biden, as his advisers believe his message on income inequality and major structural change can appeal to the same white working-class voters who make up much of Mr. Biden’s base.
The clashes could offer an opportunity for candidates who stay above the fray. While Ms. Klobuchar sparred with Mr. Buttigieg during the last debate, she’s previously sought to tamp down tensions among her opponents and avoided taking moderators’ bait to go after other candidates.
And Mr. Steyer could look to capitalize on a handful of recent polls that have shown him gaining traction in some of the early primary states.
First Published January 15, 2020, 3:47 a.m.
