But Mr. Sanders, speaking at his New Hampshire campaign headquarters, cited his lead in other, raw numbers that are effectively an expression of the popular vote in Iowa.
“Even thought the vote tabulations have been extremely slow, we are now at a point, with some 97 percent of the precincts reporting, where our campaign is winning the popular initial vote by some 6,000 votes,” Mr. Sanders said, sounding frustrated but resolute. “In other words, some 6,000 more Iowans came out on caucus night to support our candidacy than the candidacy of anyone else. And when 6,000 more people come out for you in an election than your nearest opponent, we here in northern New England call that a victory.”
His announcement immediately put him at odds with Mr. Buttigieg, who has also declared victory. On the night of the caucuses, he seized on the uncertainty to pre-emptively crown himself the winner — and has continued to do so since.
Mr. Sanders had a different take on Thursday, however: With eight candidates competing in Iowa, and a voter turnout of, by his estimation, about 180,000, he called his margin of victory “decisive.”
In unusually harsh terms — at odds from the tone his campaign struck earlier this year — Mr. Sanders also laced into the Iowa Democratic Party, calling what happened a “screw-up” and an “outrage.”
“I think what has happened with the Iowa Democratic Party is an outrage — that they were that unprepared that they put forth such a complicated process,” he said, that relied on “untested technology” and volunteers.
And he blamed the news media for putting “too much emphasis” on the state delegate equivalents, which are a measure of the estimated number of state delegates won by each candidate. In response to questions about his decision to declare victory amid inconsistencies and the call for a recanvass, Mr. Sanders argued again that he had won on the popular vote measure. “We won an eight-person election by some 6,000 votes. That is not going to be changed,” he said.
The mess in Iowa is in some ways a victory for Mr. Sanders, who has railed against the Democratic Party for years. Since 2016, when he narrowly lost to Hillary Clinton in Iowa, he and his allies have also raised questions about the caucuses and how the state party reports results. Sanders allies immediately jumped on reports that there were inconsistencies this year to express vindication and call attention to weaknesses in the process.
“The fact that we now have clear results of the popular vote is something that we fought for, that did not exist in 2016,” he said. Though he stopped short of casting doubt on the 2016 results — “I don’t want to revisit 2016,” he said — he did say there was “some supposition that we actually won the popular vote” that year as well.
In addition to declaring himself the winner on the first count — “the popular initial vote” — Mr. Sanders also said he had won on the second count, known in Iowa as realignment. “In that process,” he said, “we are now ahead by over 2,500 votes.”