Pete Buttigieg, the former mayor of South Bend, Indiana, has taken the lead in the Iowa caucus after most of the official results were released following a day-long delay in the Democratic contest.
The Iowa Democratic Party has come under heavy criticism for the 22-hour delay in releasing the result after blaming “irregularities”.
It announced that after 62 per cent of the count, Mr Buttigieg was in the lead in the rural state.
The official results showed him leading with 26.9 per cent of the vote, ahead of Bernie Sanders on 25.1 per cent.
Senator Elizabeth Warren took 18.3 per cent, former vice president Joe Biden trailed in fourth at 15.6 per cent, and Senator Amy Klobuchar secured 12.6 per cent.
The results contradicted much of the polling before the Iowa caucus on Monday, which gave Mr Sanders or Mr Biden the lead.
Mr Buttigieg, a former veteran, becomes the first openly gay candidate to come that far in the process.
He had already claimed victory on Monday night before the official results were released.
“Iowa, you have shocked the nation," Mr Buttigieg said. "By all indications, we are going on to New Hampshire victorious."
Chairman of the Iowa Democrats Troy Price apologised on Tuesday for the delay in releasing the votes.
"I apologise deeply for this," Mr Price said. "We hit a stumbling block on the reporting of the back end of the data, but we know this data is accurate."
He did not, however, give a time on when the rest of the results would be released amid shaken trust in the process and questions about verification of the results.
The Republican Party was quick to seize on the criticism aimed at the Democratic leadership.
Supporters of President Donald Trump were tweeting “rigged” in reference to the debacle, and tried to exploit the divide within the party between the leftist camp of Mr Sanders and the moderate supporters of Mr Buttigieg.
Mr Trump also weighed in.
“The Democrat Caucus is an unmitigated disaster," he said. "Nothing works, just like they ran the country.
"Remember the $5 billion Obamacare website, which should have cost 2 per cent of that. The only person who can claim a very big victory in Iowa last night is Trump."
The state of New Hampshire is set to vote next on Tuesday, followed by Nevada on February 22, then South Carolina on February 29.
Former mayor of New York Mike Bloomberg has not campaigned in the early states and is instead focusing his campaign on the big “Super Tuesday” battles on March 3.