Six of the Democratic presidential candidates will meet for a debate here Tuesday night at a time of escalating tension between Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren, the leading two progressive candidates who had tried until now to avoid attacking one another.
The Massachusetts and Vermont senators, who have been longtime ideological allies and personal friends, will meet on stage Tuesday for the CNN/Des Moines Register debate just a day after Warren affirmed what four sources said to CNN about a private conversation she had with Sanders in 2018, when she says he told her a woman could not win the presidency. Sanders has strenuously denied the claim, calling it ludicrous. His campaign later suggested Warren misconstrued the conversation.
The CNN report came after a weekend in which Politico reported that Sanders volunteers were working off a call script that portrayed Warren as a candidate of the elite who could not build a broad enough coalition to vanquish President Donald Trump in November.
Sanders said he did not know about the script until he read about it and insisted that no one would be attacking Elizabeth Warren.
But the sudden turn from the unspoken non-engagement pact of the two candidates to the aggressive jousting of the past few days reflected the deadlock in a race that is essentially a four-way tie in Iowa
Sanders, Biden, Warren and Buttigieg are tightly clustered at the top of the Democratic field in recent polling. In interviews, Iowa voters have expressed a profound sense of indecision -- driven largely by the size of the field and what they perceive as the complexity of defeating Trump in November.
At a time of international uncertainty about tensions between Iran and the United States, Biden has argued to Iowa voters that he is the candidate with the experience to smooth over relationships with leaders around the world.
On the flip side of that argument, Sanders has argued that Biden showed poor judgment in voting to authorize former President George W. Bush's decision to use military force in Iraq, which he opposed.
Sanders and Buttigieg are likely to air that criticism of Biden on Tuesday, with Buttigieg highlighting his military experience and Sanders noting his long-standing opposition to wars in the Middle East that draw resources away from the priorities of average Americans.
Tuesday's debate at Drake University will offer two long-shot candidates -- Minnesota Sen. Amy Klobuchar and businessman Tom Steyer -- their last chance to make their closing arguments before the Iowa caucuses on February 3..
The debate will begin at 9 p.m. ET on CNN.