US President Donald Trump wasted no time in pouncing on the Democratic chaos in Iowa, framing it as a victory for himself.
Mr Trump tweeted that the debacle was an "unmitigated disaster", suggesting it was proof that Democrats could not be trusted to lead.
"The only person that can claim a very big victory in Iowa last night is 'Trump'," he wrote.
Clouded by doubts on a chaotic day-after, the Iowa Democratic Party began releasing partial results of the state's first-in-the-nation presidential caucus late last night.
Pete Buttigieg took a narrow lead in the first batch of long-delayed results and former vice-president Joe Biden trailed badly in fourth place with about 62pc of precincts reporting.
US Senator Bernie Sanders was a close second and US Senator Elizabeth Warren placed third in the first results, released nearly 21 hours after Iowans poured into more than 1,600 public locations to begin the five-month process of picking a challenger to Mr Trump.
In the first results of state delegate equivalents, the data traditionally reported to determine the winner, Mr Buttigieg, the former mayor of South Bend, Indiana, had 26.9pc, Mr Sanders 25.1pc, Ms Warren 18.3pc and Mr Biden 15.6pc. Senator Amy Klobuchar was fifth at 12.6pc.
Mr Buttigieg (38) would be the first openly gay US president if elected.
While campaigns were eager to spin the results to their advantage, there was little immediate indication that the incomplete results eased the confusion and concern that loomed over the opening contest of the Democrats 2020 presidential primary season.
It was unclear when Iowa's full results would be released.
During a private conference call with campaigns earlier in the day, state party chairman Troy Price declined to answer pointed questions about the specific timeline - even whether it would be a matter of days or weeks.
"We have been working day and night to make sure these results are accurate," Mr Price said.
The leading candidates pressed on in next-up New Hampshire, which votes in just seven days, as billionaire Democrat Michael Bloomberg sensed opportunity, vowing to double his already massive advertising campaign and expand his sprawling staff focused on a series of delegate-rich states voting next month.
The party's caucus crisis was an embarrassing twist after months of promoting the contest as a chance for Democrats to find some clarity in a jumbled field with no clear front-runner.
Instead, after a build-up that featured seven rounds of debates, nearly $1bn spent nationwide and a year of political jockeying, caucus day ended with no winner, no official results and many fresh questions about whether Iowa can retain its coveted "first" status.
Iowa marked the first contest in a primary season that will span all 50 states and several US territories, ending at the party's national convention in mid-July.
Campaigning in New Hampshire yesterday, Ms Warren said she was "feeling good" about her performance in Iowa but questioned the state party's plans to release partial results.
"I just don't understand what that means, at least half of the data. I think they ought to get it together and release all the data," she said.
The Sanders' campaign told supporters that its internal monitoring showed him in the lead with nearly half the vote in.
Mr Sanders himself said late on Monday that "Today marks the beginning of the end for Donald Trump".
Mr Buttigieg essentially declared an Iowa victory.
"So we don't know all the results, but we know by the time it's all said and done, Iowa, you have shocked the nation," he said before leaving Iowa. "By all indications, we are going on to New Hampshire victorious."
Mr Biden said he was "feeling good" and predicted the results would be close. The party told campaigns yesterday that the problem was a result of a "coding issue in the reporting system" that it said had since been fixed. It said it had verified the accuracy of the collected data and said the problem was not a result of "a hack or an intrusion."
A Biden campaign representative objected to the party's plan to release partial results before checking them against paper records, saying in the conference call that the plan didn't address "growing reports" about problems on caucus night, such as precinct captains unable to get through on the phone to report results.