“It was money well spent,” said Robert Mandell, another former ambassador and Buttigieg fund-raiser.

But the impact of Mr. Buttigieg’s apparent win in Iowa was dampened by the delayed and muddled results that are still subject to a recanvass. His campaign announced he had raised $4 million in the four days afterward. That is a significant sum but still less than what rival strategists said might have otherwise been expected for winning the opening contest.

Mr. Sanders was raising money at a clip of well above $1 million per day online in early February, according to an estimate based on figures released by his campaign. And that was before he won the New Hampshire primary. Ms. Warren’s campaign told supporters this week she had raised $5 million in the nine days following the Iowa caucuses. Neither senator is holding traditional fund-raisers for large donors.

One of Mr. Buttigieg’s events will be on Feb. 23 at the home of Representative Don Beyer, a Virginia Democrat and the first member of Congress to endorse him, with five other congressional co-hosts. Three days later, he will hold three fund-raisers across Florida — which does not hold its primary until March 17 — including one in Palm Beach whose hosts include Cynthia Friedman, a longtime Democratic contributor.

The campaign had sent invitations to even more events, including in Atlanta and Charlotte, N.C., on Feb. 27 — the $500 level ticket is listed as sold out online for the Atlanta gathering — but Buttigieg aides said those events were being rescheduled.

Mr. Buttigieg is not alone on the fund-raising circuit. Former Vice President Joseph R. Biden Jr. organized a conference call with his national finance committee after his fifth place New Hampshire finish to reassure skittish donors. He has upcoming fund-raisers in Colorado, Nevada and South Carolina, the latter two in states that vote later this month.

On Thursday, Mr. Biden held two events in New York that drew a notable group of Wall Street contributors. Organizers said the events raised almost $800,000, a large haul for a candidate who had sagged to fourth and fifth place in the first two contests. Mr. Biden also said on “The View” this week that he was raising about $400,000 per day in online donations.