Mr. Buttigieg’s fund-raising haul of more than $7 million came from 158,550 donors, with an average contribution of $36.35, Mr. Buttigieg said in a video posted online late Monday. He added that 64 percent of the total came from contributions under $200.

Mr. Buttigieg, who is technically still only exploring a campaign, said last month that he had exceeded the 65,000 donors needed to garner a spot on the Democratic National Committee’s primary debate stage, even as some better-known rivals have suggested they do not yet have that many.

Mr. Buttigieg’s fund-raising jumped after he appeared in a CNN town hall-style event earlier in March and impressed Democratic activists and donors, as he fielded questions in rolled-up white shirt sleeves and a blue tie. His campaign announced that he raised $600,000 in the 24 hours after his appearance.

Lis Smith, a spokeswoman for the campaign, described the televised forum as a turning point. Interest in Mr. Buttigieg had been rising before then, she said, but the CNN event “really brought everything to the next level.”

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An openly gay veteran and former Rhodes scholar, Mr. Buttigieg has made numerous appearances on national television in recent weeks seeking to lift his political profile. Later last month he told supporters via email that he was setting a $500,000 fund-raising goal by the end of the month. He hit the figure within 24 hours, his campaign said. He set another $500,000 goal. Again, he reached it in about 24 hours.

Mr. Buttigieg’s fund-raising is particularly noteworthy because he began his campaign with only a modest email list from which he could solicit donations — a stark contrast with rivals like Mr. Sanders and Mr. O’Rourke, who built huge followings in their prior campaigns for president and Senate.

In addition, Mr. Buttigieg has spent relatively little money on advertising on Facebook, which many candidates use to expand their email lists.