Delays hit the Iowa caucus for Democratic candidates

US election officials are being extra-cautious as delays hit the Iowa caucus - which could decide who will take on US President Donald Trump in the election later this year. 

Iowa is the first state to decide who it wants to run for the presidency and since 2000, whoever has won there has gone on to win the Democratic nomination.

After more than a year of debates, speeches, entrances and exits, Iowa caucus-goers finally got to weigh in on which Democratic candidate should challenge Trump.

On the far-left is 78-year-old Bernie Sanders, who is recovering from a heart attack but has a laser-like focus on the prize that eluded him four years ago. 

"We are going to create a government and economy that works for all of us, not just the 1 percent and billionaire campaign contributors," he said.

His crowds are large and his supporters young - plus they're fanatically loyal to his cause.

But Elizabeth Warren is also after the fired-up Democratic base. 

Pete Buttigieg has been this year's surprise, 38 years old, gay and gaining momentum.   

"I want you to join me in visualising how it's going to feel that first time the sun comes up over Iowa and Donald Trump isn't the president of the United States," he said.

Then there is Joe Biden, much more moderate and claiming only he can take on Trump and win.

"We choose science over fiction, we chose unity over division, and we choose truth over lies," he said.

However, he could be the big loser here. 

Iowa's caucus is important because since 2000 every Democratic candidate who won there went on to compete for the presidency.

The mid-western and deeply rural state is the first to pass judgment on who should take on Trump. 

This year a record turnout and unprecedented unity are both being hailed as good signs for the Democrats to ensure Trump doesn't get a second term.