With less than three weeks to go before the Iowa caucuses, tensions escalated between two of the leading Democratic candidates and were on display on national television at a debate in Iowa.

We’ll catch you up on this and other moments you may have missed from a very busy week.

A timeline of the Sanders-Warren tension

For almost a year, Senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts had a tacit nonaggression pact. But not anymore.

The trouble started last weekend with the publication of a script that volunteers on the Sanders campaign had been using, telling voters that Ms. Warren appealed to “highly educated, more affluent people” and brought “no new bases” to the party. Then, on Monday, Ms. Warren said that Mr. Sanders had told her in a private meeting in December 2018 that he did not believe a woman could win the presidency — a claim Mr. Sanders vehemently denied.

The disagreement came to a head on Tuesday. During the debate in Iowa, the two senators had a brief, relatively cordial exchange in which Mr. Sanders again denied making the remark and Ms. Warren pivoted to a broader point about women’s “electability.” But afterward, as the candidates were mingling onstage, Ms. Warren confronted Mr. Sanders directly.