The Iowa caucuses began at 7pm Central - 8pm Eastern - with Bernie Sanders ahead in polls but by a tiny margin

But by 11pm with no results released by the Democratic party, it became clear that the caucus was in crisis

Iowa Democratic Party issued a panicked statement denying it had been hacked but saying there were 'inconsistencies' in how results were reported

An app which was supposed to be the system for reporting was a 'mess' and results had to be phoned in

Party said it was carrying out 'quality checks' on results and offered no timescale for when there would be actual results

Party was for the first time releasing both the final number of delegates each candidate gets and the underlying data behind it - but that appears to be where the 'inconsistencies' lie

There was strong interest in the caucuses, with Polk County, the largest area and home to Des Moines, printing extra voter registration paperwork

Because of the complicated system it is possible for the person with the most delegates to not have the largest share of vote - so more than one campaign could declare itself winner

Entrance poll results showed that defeating Donald Trump is top of the list of concerns for caucus-goers

Health care is the most important single issue with six in 10 backing single-payer public healthcare, and nine in ten Medicare for all - the poll allowed them to express support for both

Who won the Iowa Democratic caucus will not be known until later Tuesday as an embarrassing fiasco with a hi-tech app left officials counting voted by hand and admitting they have found 'inconsistencies.'

Voting officials admitted a string of failures in a panicked conference call at 1am Central time (2am Eastern), saying the catastrophe engulfing the first-in-the-nation contest saw their app collapse, the backup call center not working, and local officials fail to record results properly.

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The Democrats refused to take questions but said they would have results 'later on Tuesday,' after enduring a stormy meeting with campaigns, one of whom - Pete Buttigieg's - declared victory while another - Joe Biden's - said the results could not be trusted at all.

Caucusing around the state started at 7pm Central Standard Time. Three hours later, not a single precinct's results were officially in - prompting an admission that there was a crisis.

'We found inconsistencies in the reporting of three sets of results. In addition to the tech systems being used to tabulate results, we are also using photos of results and a paper trail to validate that all results match and ensure that we have confidence and accuracy in the numbers we report,' Iowa Democratic Party Communications Director Mandy McClure said in a statement. 'This is simply a reporting issue, the app did not go down and this is not a hack or an intrusion.'

The underlying data and paper trail is sound and will simply take time to further report the results,' McClure added. Earlier, other Iowa officials had pointed a finger at the app.

Des Moines County Chair Tom Courtney told the Associated Press that it was 'a mess' and organizers were having to call in the results to the party.

CNN reported that party officials are meeting with representatives from the campaigns.

This is the first year that three separate results will be released to the public. The number of caucus-goers who initially came to support candidates, then the second vote - how caucus-goers re-aligned if their candidates weren't viable. Finally, the number of delegates won by each candidate will be reported.

Each of the precincts is using 'presidential preference' cards for the first time, so there will be a paper trail of the vote.

At around 10:15pm Sen. Amy Klobuchar, who anecdotally had a good night, rushed to the mic - the first candidate to do, prompting Joe Biden then Elizabeth Warren then Bernie Sanders to do the same.

Following after the first four, former South Bend Mayor Pete Buttigieg made the boldest pronouncement.

'Iowa you have shocked the nation,' Buttigieg said. 'Because by all indications, we are going on to New Hampshire victorious.'

Klobuchar merely told her crowd she had defied expectations.

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'We know there are delays but we know one thing - we are punching above our weight. My heart is full. We feel good tonight,' Klobuchar said from the downtown Des Moines Marriott hotel.

How the results will be done: The hand-filled ballots which are now going to be used by the Democrats to work out the results of the Iowa caucus

What is going on? Bernie Sanders supporter David Soll, who had traveled from Rockford, Illinois, to campaign for the socialist candidate, was among those caught up in the results fiasco

First to the microphone: Amy Klobuchar rushed in front of the cameras as the scale of the fiasco became clear and said that while she did not know the results, she was sure her campaign had 'punched above our weight'

Why are we waiting? Pete Buttigieg supporters at Drake University, Des Moines, are caught up in the delay

Wait it out: Joe Biden's supporters wait to find out what is happening as the Democratic results are plunged into chaos

Please someone tell me what is going on? A Joe Biden supporter tries to find out the cause of the unprecedented delay

Sorted out: The crowd at Drake University back by candidate in the first round with a count then taking place

Second round under way: Joe Biden's supporters canvas for more among Pete Buttigieg supporters

Won't you be my caucus-goer? At Algona High School in Algona, Elizabeth Warren was not 'viable' meaning her supporters were free to back other candidates in the second round, with Amy Klobuchar supporter Keith Dwire trying to persuade Warren backer Jo Morgan

Down - but is he out? A left-over Joe Biden sign at the Drake University Olmsted Center in Des Moines

At a caucus site several miles away, in Norwalk, Iowa, Klobuchar defied expectations and came in second place, DailyMail.com observed. Overall, she got 34 votes to Sen. Bernie Sanders' 32. Former South Bend Mayor Pete Buttigieg won that site with 55 votes, while former Vice President Joe Biden only had 12 and wasn't viable to win delegates.

'I have a strong feeling that at some point the results will be announced,' Sanders told his crowd gathered at a Holiday Inn conference center near the Des Moines airport. 'And when those results are announced I have a feeling we are going to be very, very well here in Iowa,' he boasted.

There appeared to be strong - if not record-breaking - interest as the caucuses got under way.

Organizers of a precinct site in downtown Iowa City said the start of the caucus had to be delayed by more than an hour, as hundreds of people were still waiting to check in or register to vote. Inside the Englert Theatre near the University of Iowa, 500 first-floor seats were mostly full and organizers were opening an additional 200 seats in the balcony.

In Polk County, Iowa's largest county and home to the capital city, Des Moines, Democratic county party chairman Sean Bagniewski said the party had printed tens of thousands of extra voter registration forms but some precincts were running out.

'We're making copies and deliveries to get them covered, but this caucus is gonna be the big one,' Bagniewski tweeted.

About 170,000 turned out in 2016. The high-water mark for the contest was the 2008 Iowa Democratic caucuses, when nearly 240,000 participated and Barack Obama defeated Hillary Clinton and John Edwards.

The caucuses come as Sanders' campaign seems to be gaining steam, while that of Vice President Joe Biden - long considered the party's frontrunner - sputters.

Late Monday night, Biden made no effort to declare victory.

'We’re going to walk out of here with our share of delegates,' Biden said when he talked to supporters at Drake University in Des Moines. 'But we feel good about where we are.'

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Biden's backers were bracing fo a tough result, eager to take the primary fight to South Carolina, which has a large share of black voters and where Biden has performed well in polls.

'The Iowa Democratic Party is working to get these results and get them straight,' the former vice president also told the crowd. 'And I want to make sure they’re very careful with their deliberations.' His campaign had also sent a letter to the state's Democratic Party.

President Trump's campaign reacted to the chaos with glee.

'Democrats are stewing in a caucus mess of their own creation with the sloppiest train wreck in history. It would be natural for people to doubt the fairness of the process. And these are the people who want to run our entire health care system?' said Brad Parscale, the president's 2020 campaign manager. 'Tonight President Trump posted a record performance in the well-run GOP Iowa caucuses with record turnout for an incumbent.'

Fired up: Elizabeth Warren uses a bullhorn at Roosevelt High School in Des Moines. She went in to the race behind Bernie Sanders in the polls

Please get behind me: Elizabeth Warren addresses her and Bernie Sanders' supporters at Roosevelt High School, Des Moines

Someone's with her: Elizabeth Warren greets a supporter at a caucus in Des Moines. In common with other candidates she toured multiple venues as people voted

Show of support: Joe Biden's supporters show who they back at Drake University in Des Moines

No enthusiasm gap: Bernie Sanders' supporters get ready for the caucus to become an exercise in persuasion

Ready to go: Caucus-goers in a fire station in Kellogg, wait to show their support for the candidates

Ready for the caucus: At Hoover High School, voters headed to the basketball court to show their support for their favored candidate

Ready for the caucus: At Hoover High School, voters headed to the basketball court to show their support for their favored candidate

Support on show: An Elizabeth Warren supporter makes her position clear at a caucus at Roosevelt High School, Des Moines

Can I count on you? Elizabeth Warren speaks to voters - and one of their children - at a Des Moines caucus

Feeling the Bern: A Sanders volunteer is ready to persuade fellow Iowans at the Maple Grove Methodist Church in Des Moines

How it works: The Kellogg fire station is ready with locals asked to line up under their first preference. Anyone who backs a candidate under 15% is then asked to move to one of the candidates who scored over 15%.

Here to vote: Registration at Roosevelt High School in Des Moines, just before the 7pm starting point for the caucus

Ready for Bernie: Volunteers prepare to try to persuade caucus-goers that they should back their candidate, who is ahead by a tiny margin in the polls

Read for Joe: Biden's campaign is concerned about the rise of Bernie Sanders, with one of his closest allies, former Secretary of State John Kerry, unleashing a foul-mouthed tirade against the socialist

Bernie Sanders won the support of 14 out of the 15 caucus-goers at the 'satellite' caucus in Ottumwa, Iowa Monday at noon. The group was largely Ethiopian immigrants who work at a nearby pork processing plan

There had always been the potential for confusion with the new system of reporting caucus results: the Iowa Democratic Party will release the breakdown of how many delegates candidates have obtained, and also the underlying raw data - which could allow multiple campaigns to claim 'victory.'

Sanders had already won the first delegates of the Iowa caucus, largely thanks to a group of Ethiopian-American immigrants who work at a pork processing plant.

The Intercept reported Monday that at a satellite caucus site in Ottumwa, Iowa - about an hour and a half southwest of Des Moines - 14 of 15 caucus-goers selected Sanders as their choice.

A lone participant backed Sen. Elizabeth Warren, who wasn't viable at this caucus location because she didn't amass 15 per cent of those gathered.

As caucus-goers arrived, the issue of defeating President Donald Trump in November's election was at the top of their minds according to preliminary findings by the National Election Pool (NEP).

The NEP, a consortium of news organizations including Reuters that runs election-day polling through Edison Research, found most caucus-goers were simply looking for a winner instead of someone who agrees with them on the issues.

Among the key findings were:

Six in 10 caucus-goers said they were looking for a Democratic nominee who they think can beat Trump. About four in 10 said they wanted a nominee who agrees with them on major issues.

Three in 10 said they were attending the Iowa caucuses for the first time, which appears to be below that of 2016. Four years ago, 44% of people attending the Iowa caucuses said they were doing so for the first time. In 2008, 57% said they were new to the Iowa caucuses.

Nearly a third of Democrats said before entering the caucuses that they picked their candidate in the last few days. That appears to be higher than the number of late deciders in 2016. Four years ago, 16% of caucus-goers said they had made their choice in the last month or earlier.

Healthcare was the issue that mattered most to Iowa caucus-goers. About four in 10 said that was the issue they cared most about when thinking about picking a nominee. Two in 10 said it was the climate, another two in 10 said it was income inequality and one in 10 said it was foreign policy.

The entrance poll also asked Democrats about which candidate they were supporting for the nomination. The selections are not predictive of the outcome, however, given that many Democrats will change their preferences if their chosen candidate does not win enough support in the caucuses.

At caucus sites across the state, volunteers were in place for hours before the start of voting. There were a few early caucuses outside the state, the furthest known one in the former Soviet republic of Georgia.

Officially, it was also the first Iowa caucus and held in the capital Tbilisi, over traditional Iowan fare - pizza with ranch dressing, according to reporter Joshua Kucera, who was on-site.

Other caucus locations include Glasgow, Scotland, Brooklyn, New York, Washington, D.C. and several places in Florida and California, among others.

Monday's caucuses mark the first official votes of the 2020 Democratic presidential primary after more than a year in the making.

Sanders' late polling uptick has spooked the Democratic establishment.

The most dramatic example of party fears being expressed came from an overheard phone call from former Secretary of State John Kerry, in the Hawkeye State as a surrogate for Biden. Kerry was the Democrats' 2004 nominee and lost.

NBC News reported Sunday that Kerry was workshopping what he could do to get into the 2020 race because of 'the possibility of Bernie Sanders taking down the Democratic Party - down whole.'

'Maybe I'm f***ing deluding myself here,' Kerry said.

Once the story came out, Kerry denied that he was mulling a 2020 bid in an expletive-laden tweet, which he later deleted, posting a cleaner version.

Iowa polls have shown Sanders and Biden neck-and-neck, though have given the Vermont senator a slight edge.

The Real Clear Politics polling average on Monday showed Sanders with a 4 point lead over the former vice president.

How to understand the Iowa Caucuses (and why there may be more than one 'winner') The Iowa caucuses are essentially small local meetings where neighbors and strangers stand up to show their support for a particular candidate, and to persuade others to join them. Iowa's 41 national delegates are up for grabs, but the real stakes for the candidates are all about momentum. The caucuses are the first opportunity for Democrats to express their preferences in what´s been a long and tumultuous primary. They set the tone for the monthlong sprint through the early primary states, after which the field of candidates is typically culled. The winner usually receives a boost in media attention and fundraising that can propel them through subsequent contests. An unexpectedly bad performance, meanwhile, can hobble a candidate. Attendees hold letters reading Caucus during a campaign event in Coralville, Iowa The caucuses don´t always pick the eventual nominee, but for Democrats they´ve been more predictive - every winner since 2000 has gone on to become the Democratic nominee. And historically, they´ve been known to catapult underdog candidates´ campaigns to prominence - like they did with Barack Obama in 2008, or Jimmy Carter in 1976. WHERE AND WHEN DO THEY TAKE PLACE - AND WHO PARTICIPATES? The caucuses begin at 7 p.m. CST on Monday. Democrats gather in school gymnasiums, union halls and community centers - known in caucus parlance as precincts. There are 1,678 precincts in Iowa this year and an additional 99 satellite precincts, which are for caucuses held outside of the state or at different times of the day and in locations that may be more accessible to those with disabilities or those who have to work during the main event. Some precincts could have hundreds of Iowans show up, and some may have fewer than 10. The 2008 Democratic caucuses set a record when nearly 240,000 Iowans turned out; this year, party operatives are expecting turnout to be big, but likely not record-breaking. Any registered Democrat who will be 18 by election day can participate, which includes 17-year-olds with an upcoming birthday. And Iowans can newly register or switch their party registration at their caucus site the day of - so campaigns have been courting disaffected Republicans and new voters across Iowa. WHAT HAPPENS AT A CAUCUS? There are essentially two rounds of voting in the caucuses. When all the caucusgoers at a precinct have signed in, the attendees elect a caucus chair, who directs the proceedings. Representatives of the campaigns have an opportunity to stand up and give a last-minute pitch for their candidate, and then the caucuses begin, with a process known as the 'first alignment.' That´s where attendees gather in the designated area for their favored candidate. In most precincts, any candidate that receives the support of 15% of the people in the room is considered 'viable' and moves on to the next round of voting. Caucusgoers who chose a viable candidate on their first round are locked in and can´t choose a new candidate on the second. Democratic presidential candidate former South Bend, Ind., Mayor Pete Buttigieg's shadow is cast on the Iowas state flag in Coralville, Iowa Supporters of candidates who didn´t meet that threshold, however, have four options: They can support a viable candidate, or join with supporters of another non-viable candidate close to 15% support to get them to viability. Alternately, they can try to entice supporters of other non-viable candidates over to theirs to get them over the threshold. Or, they can go home. This part of the caucuses - known as realignment - is the most crucial, and typically the most chaotic, portion of the night. Well-organized campaigns have volunteers, staffers and surrogates working the room, trying to win over caucusgoers from opposing campaigns. It´s part of the reason why having staff and surrogates who know their area and have built a community there is so important for the campaigns. At the end of realignment, the caucus chair takes a final count of the room, and transmits the numbers to the Iowa Democratic Party. Changes from 2016 will allow for additional reporting of caucus results HOW ARE THE RESULTS CALCULATED? The results in each precinct are used by the Iowa Democratic Party to calculate what´s known as the 'state delegate equivalent,' or how many delegates each candidate gets at the Iowa Democratic Party convention. That number ultimately translates to how many of Iowa´s 41 national delegates each candidate gets at the national convention. HOW ARE THIS YEAR´S CAUCUSES DIFFERENT FROM YEARS PAST? For the first time, caucusgoers will record their choices on a slip of paper, which they´ll sign to certify their support. The caucus leaders will collect those presidential preference cards and turn them into the Iowa Democratic Party, and they´ll be used if any candidate requests a recount. This year, there are only two rounds of alignment, rather than the multiple rounds in years past, and supporters of a viable candidate after the first alignment are locked in to that candidate. In previous caucuses, every attendee could choose a new candidate on each realignment. The satellite caucuses are new, and the Iowa Democratic Party is allowing attendees to check in early rather than at their precinct site, a move aimed to cut down on the long lines and wait times in years past. But the biggest change is the change in how the Iowa Democratic Party will report its results. Previously, they only released the state delegate equivalent numbers; now, they´re releasing the raw totals from the first and second alignments, as well as the state delegate equivalents. The Associated Press will be deciding the winner based on state delegate equivalents - but with more data being released, the campaigns have signaled they plan to spin the numbers in their favor, whatever the eventual result. - Associated Press

This is how they do it: Caucus goers fill in preference cards as a permanent record of votes

What counts: At the West Des Moines Christian Church, an election official counts up support

To young to back me: Elizabeth Warren greets a young supporter at Roosevelt High School, Des Moines

Rivals: A Joe Biden and a Pete Buttigieg precinct captain go head to head at Maple Grove Methodist Church in West Des Moines. The two moderates are both behind Bernie Sanders

Read for Buttigieg: The former South Bend, Indiana, mayor, has his supporters ready to push for support in Roosevelt High School

Something to show for it: One voter was knitting her way through the caucus at Maple Grove Methodist Church in West Des Moines

Sen. Amy Klobuchar seems to be benefiting from late-breaking Iowa voters. She's shot up in the polls in the past week and her events are attracting crowds numbered in the hundreds

For months, former South Bend Mayor Pete Buttigieg has also had a strong showing in the Hawkeye State - meaning Monday night's caucuses could end up being a five-way split

WHAT THEY SAID ON THE WAY IN Preliminary results from AP VoteCast, a survey of 2,795 voters conducted for The Associated Press by NORC at the University of Chicago. A STRONG OPPONENT TO TRUMP About 8 in 10 Iowa caucusgoers expressed anger toward the Trump administration. Beating Trump in November, along with providing strong leadership, outranked other qualities as most important in a nominee. More than 8 in 10 Democratic caucusgoers said it was very important the party´s nominee can defeat Trump. Close to as many said they find it highly important to nominate someone who will be a strong leader. WHAT ELSE VOTERS WANT Three-quarters of likely caucusgoers said it's very important their choice for the Democratic nominee cares about people like them, while nearly two-thirds said it's very important the party´s nominee have the best policy ideas. Six in 10 Democratic voters said it was very important the Democratic nominee will work across party lines. Fewer Democrats - about half - placed significant importance on a nominee who has the 'right experience.' THE HEALTH CARE DEBATE Roughly 4 in 10 likely caucusgoers identified health care as their top issue. Seven in 10 supported a proposed single-payer health care plan, which would change the health care system so that all Americans receive insurance from a government plan instead of private insurance plans. At the same time, nearly 9 in 10 favor the proposal for an optional government plan that any Americans could buy into if they wanted. A wide share - about 6 in 10 - expressed support for either plan, but roughly a quarter favored 'Medicare for All' and opposed 'Medicare for all who want it.' Only about 1 in 10 expressed the opposite opinions, in favor of a public option but opposed to a single-payer system. CLIMATE CHANGE Along with health care, climate change was identified as the top issue facing the country by 3 in 10 Iowa voters.

Recent polls also show Sen. Amy Klobuchar, a Minnesota Democrat, gaining steam - as a number of late-breaking Iowa voters are flocking her way.

Additionally, Sen. Elizabeth Warren and South Bend Mayor Pete Buttigieg have, for months, had strong interest from voters in the state - meaning it could be a five-way race.

On top of that, the way the Democrats caucus in Iowa is unique.

Once the Democrats are inside the caucus location they gather in groups with their candidate of choice. Candidate must have a threshold of 15 per cent to be viable, so a lot of politicking happens each caucus night - making the results incredibly difficult to predict.

This year, too, the number of initial supporters who came out for each candidate will be reported publicly.

Candidates like Andrew Yang, who has been polling under 15 per cent the whole time, could point to the original vote total to prove that the campaign has enough support to continue on.

In the past, Iowa has been where many a campaign died.

One example, was Biden's 2008 effort. While he came in fifth place in the caucuses, because of the 15 per cent rule his vote total only amounted to 1 per cent. He dropped out the day after.

Impeachment has also cast an odd spell over the run-up to the caucuses this year.

It kept three leading contenders - Sanders, Warren and Klobuchar - off the ground for days at a time.

The fourth U.S. senator running for president, Colorado's Michael Bennet, has bypassed Iowa and has been focusing on New Hampshire, which holds a primary next week.

Warren's campaign made-do by deploying her 20-month Golden Retriever Bailey, escorted by her husband Bruce Mann, to campaign stops last week.

Bailey even took over Warren's famous selfie lines once the Massachusetts senator was back in state, so she could cover more ground.

Sanders' campaign utilized his wife Jane and a number of buzzy surrogates including the three so-called 'Squad' members who've backed his campaign.

Rep. Alexandria Ocasio-Cortez hosted campaign events one weekend Sanders was away, while Reps. Rashida Tlaib and Ilhan Omar came to Iowa this past weekend.

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The Democratic caucuses in Iowa are unique. Caucus-goers gather in groups to back their chosen candidates. If their group doesn't amount to 15 per cent of those at the caucus site, they can choose to be redistributed to a viable candidate.

The newly-divorced Omar even brought her boyfriend, who also recently split from his spouse.

Tlaib's decision to encourage a crowd of Sanders supporters in Clive, Iowa Friday night to boo the Democrats' 2016 nominee Clinton showed more splinters in the party.

By Saturday morning, Tlaib was walking back her actions.

Clinton has popped her head back into the fray to disparage Sanders, who was her primary rival last cycle.

In a documentary, she said of Sanders: 'Nobody likes him, nobody wants to work with him, he got nothing done. He was a career politician.'

'It's all just baloney and I feel so bad that people got sucked into it,' the ex-Democratic nominee added.

She's said more recently that she still stands by those comments.

Overall, 11 Democrats are currently running for president.

Former Rep. John Delaney - who was the first Democrat to announce his bid - dropped out Friday and encouraged Iowa voters to back a moderate choice.

His campaign bus has been repurposed to promote D.C. statehood on the day of the caucuses.

Former New York City Mayor Michael Bloomberg is skipping the first caucus and primary states, focusing on races on March 3 - dubbed 'Super Tuesday' for how many states vote.

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The other billionaire in the race, Tom Steyer, campaigned across Iowa, but is only averaging 3 per cent support in the polls.