“I just always want to be careful about how we spend our money,” Ms. Warren told reporters in New Hampshire on Wednesday.

Ms. Warren’s campaign told supporters in an email on Tuesday that the Iowa Democratic Party’s inability to announce any results on Monday night had muted whatever financial boost she could have received from the caucuses. “We didn’t get a big night of exciting news coverage about them (or the late-night boost in fund-raising that usually comes with it),” her campaign wrote.

As for Mr. Biden, he began 2020 with the least cash on hand of any of the four top candidates — less than $9 million — and his apparent fourth-place finish in Iowa already had some in the Democratic establishment skittish about his prospects.

His campaign had said ahead of the caucuses that January was his “strongest month of fund-raising since launch.” An analysis of Federal Election Commission records indicates that his January total was somewhere between about $8 million (his previous high in October 2019) and $9.7 million (his April total).

On Wednesday, Mr. Biden was also moving around his ad reservations, with about $150,000 cut from South Carolina and reinvested in Nevada, according to Advertising Analytics. Nevada will hold its caucuses on Feb. 22, and South Carolina has its primary on Feb. 29.

The need for cash is apparent from Mr. Biden’s schedule: In the days after the New Hampshire primary next week, he has no less than four fund-raisers, including two in New York, one in Denver and one in Reno, Nev.