While his financial strength has been apparent for many months, Mr. Buttigieg has seen his standing in the race improve more recently, with polls in Iowa showing him in a formidable position as the Feb. 3 caucuses approach. But he still faces significant questions about his ability to broaden his base of support beyond white voters.

In a memo released Wednesday, Mr. Buttigieg’s campaign manager, Mike Schmuhl, wrote that Mr. Buttigieg had “solidified himself as a top-tier presidential candidate” in the fourth quarter. He added that Mr. Buttigieg did so “not by tapping into the fund-raising list or bank account of a sitting senator or someone who had run for president before,” making what appeared to be veiled references to Senators Elizabeth Warren of Massachusetts and Bernie Sanders of Vermont, two rivals in the primary race.

Mr. Schmuhl said the campaign’s staff had grown to more than 500 people nationwide, with 65 field offices in early voting states. In Iowa alone, he said, the campaign now has 35 offices and more than 100 organizers.

Mr. Buttigieg’s campaign did not say how much cash it had on hand.

The fourth quarter, which began Oct. 1 and concluded on Tuesday, is the last fund-raising period for which Democratic presidential candidates will have to disclose their numbers before the Iowa caucuses, and Mr. Buttigieg was the first candidate to announce how much he had raised. The candidates are required to report their fund-raising and spending for the quarter to the Federal Election Commission by Jan. 31.

Mr. Sanders announced on Wednesday that he had received more than five million donations since entering the race, though he did not say how much he had raised in the quarter. (Mr. Sanders reached two million donations, the milestone that Mr. Buttigieg’s campaign cited on Wednesday, in July.)