"What I wanna do today, three days late, is to thank the people of Iowa for the very strong victory they gave us for the caucuses Monday night," Sanders said.
He acknowledged he was disappointed to be making the declaration to reporters at a campaign office in a strip mall in New Hampshire, instead of to voters in Iowa, but suggested that it was the right move compared to rival Pete Buttigieg, who made his own declaration of victory in Iowa on Monday night, before any results had been released.
So far, 97 percent of Iowa caucus results have been released. NBC News has not called a winner in the contest.
As of Thursday morning, Buttigieg, the former mayor of South Bend, Indiana, was clinging to the narrowest of leads with 26.2 percent and Sanders at 26 percent. Sen. Elizabeth Warren, D-Mass., was running behind the pair of leaders at 18.2 percent. Former Vice President Joe Biden had 15.8 percent, Sen. Amy Klobuchar, D-Minn., was at 12.2 percent and other candidates were in low single digits.
Iowa Democratic caucus results are not actual votes cast. The percentages, based on partial returns of the estimated number of state convention delegates won by each candidate through the caucus process, are known as state delegate equivalents.
In a different measure, voters' initial candidate preference at the caucuses, Sanders had 24.7 percent, or 42,672 votes, and Buttigieg took 21.3 percent, or 36,718 votes.
"When 6,000 more people come out for you than your nearest opponent, we here in northern New England call that a victory," the Vermont independent said.
In yet another measure, voters' reallocated preference, Sanders had 26.5 percent, or 44,753 votes, and Buttigieg had 25 percent, or 42,235 votes.
The reallocated preference is the raw tally taken after the caucus process known as realignment. If a caucusgoer's initial candidate preference did not receive enough support to meet the precinct location's viability threshold (15 percent in most caucus locations), the caucusgoer is allowed to shift his or her support — or realign — to another candidate who did attain viability.
Sanders would not call for a recanvass of the results, as Democratic National Committee Chair Tom Perez did in a tweet Thursday.
Sanders blasted the Iowa Democratic Party, calling the delay an "outrage," but did not go as far as to call for an end to Iowa’s special first-in-the-nation status as a whole.
"I think what has happened with the Iowa Democratic Party is an outrage," Sanders said. "That they were that unprepared, that they put forth such a complicated process, relied on untested technology."
Sanders was pressed by reporters on why he is declaring victory now, instead of waiting for the full results to be made public.
"I would hope given the fact that we have waited three days, and now there is the talk of another recount, you know, maybe we might want the decisions of the Iowa caucus before the November election," Sanders said dryly.