Pete Buttigieg rising in polls as Democrats battle for edge in historically important Iowa rally

Candidates scrap for momentum at event that proved to be turning point for Barack Obama

Democratic 2020 US presidential candidate Mayor Pete Buttigieg speaks at a Democratic Party fundraising dinner on Friday (Reuters)

Democrats continued to drive a wedge between moderates and progressives at a major rally in Des Moines, Iowa as Pete Buttigieg emerged as an unlikely second-place contender in the race for the state’s support.

The Liberty and Justice Celebration Dinner is the biggest campaign event in an early voting primary state – and one that has helped turn the tables for candidates of the past.

It was on the same stage Barack Obama defied expectations to build momentum for his run for the presidency in 2008, while John Kerry turned his primary campaign around at the event to win the state’s vote in 2004.

And on Friday, as democratic candidates pit the party’s progressive wing against its moderates, Mr Buttigieg used the platform to reinforce his centrist credentials while presenting himself as a younger alternative to the struggling campaign of Joe Biden.

The former US naval reserve officer has invested heavily in the state, and his supporters were among the loudest at the Des Moines event as he said he vowed to “stand amid the rubble, pick up the pieces of our divided nation and lead us to real action to do right by Americans who have waited far too long”.

In a call for unity and optimism, he added that he had "seen in the dust of a war zone Americans who have nothing in common besides the flags on our shoulders learn to trust each other with our lives" and "seen in the ruins of factories, my city answer those who said we were a dying community by rising up together to build a better future".

The Mayor of South Bend, Indiana, has emerged as an unlikely contender to Elizabeth Warren in the state. While maintaining a firm fourth place showing in national polls, a recent survey of likely caucus voters carried out by Iowa State University has moved Mr Buttigieg into second place with 20 per cent support.

Ms Warren, who remains Iowa’s frontrunner while holding a second place position nationally, used her time at the podium to appeal for sweeping change in an aside at moderates like Mr Biden and Mr Buttigieg.

“If the most we can promise is business as usual after Donald Trump, then we will lose," she said, adding that "It's easy to give up on a big idea, but when we give up on a big idea, we give up on the people whose lives would be touched by that big idea,"

"Anyone who comes on this stage and tells you to dream small and give up early is not going to lead our party to victory."

However, with the national momentum in her favour, Ms Warren proved a target for a number of tempered attacks from the party’s centre – with her proposals for universal healthcare a central point of disagreement.

Mr Biden responded to Ms Warren’s commitment to spend more than $20trillion over the next decade to health services by saying his Obamacare-based plan would be covered without "increases in taxes for the middle class”, adding “None. None. None."

The former Vice President, who remains the national frontrunner despite his poll numbers dropping, leaned on his experience at the event, adding: "The next president is going to be commander in chief of a world in disarray. There's going to be no time for on-the-job training."

Alongside New Hampshire, Iowa is the first to make its choice of candidate known – making it an important bellwether for the run of primaries leading into the Democratic convention.

Over the last 47 years only one candidate, Bill Clinton, has won the Democratic nomination without winning either of the two states.

In particular it has proved an important stepping stone in disruptive candidacies. An unexpected win in the state in 2008 provided key momentum to Barack Obama’s campaign for the White House, while in 1976 the then-outsider Jimmy Carter pulled ahead in a crowded field to win the state’s nomination and, ultimately, the presidency.