Former Vice President Joe Biden maintains the lead in the Iowa Monmouth survey with just five days to go before the Hawkeye State caucuses.

Polling data released Wednesday shows Biden with 23 per cent support among likely Iowa caucus-goers. Nipping at his heels is Sen. Bernie Sanders with 21 per cent support.

Former South Bend Mayor Pete Buttigieg, who had once overtaken Biden in the state, is in third with 16 per cent, followed by Sen. Elizabeth Warren at 15 per cent.

The only other candidate earning double-digits is Sen. Amy Klobuchar, with 10 per cent. Klobuchar has gained ground from the 3 per cent she was registering in August.

Klobuchar's climb in the polls is how her campaign responded to a New York Times report that said Biden's campaign had reached out to see if they could come together for a caucus agreement - as a way to blunt the momentum of the more progressive Sanders.

Former Vice President Joe Biden maintains a lead in Iowa a Monmouth University poll shows, with just five days to go before the Iowa caucuses - the first time voters register their preferences in the 2020 Democratic primary

New polling from Monmouth University shows Joe Biden maintaining his lead, with Sen.Bernie Sanders nipping on his heels. Pete Buttigieg, Elizabeth Warren and Amy Klobuchar follow

Sen. Amy Klobuchar of Minnesota has gained ground. The new poll shows she's at 10 per cent support, as her campaign rebuffed a New York Times article that said Biden's campaign tried to come to an agreement with hers, a fellow moderate

A potential Biden-Klobuchar alliance could blunt the momentum of Sen. Bernie Sanders. The new Monmouth poll has Sanders in second place, having gained 13 points in Iowa since August. Other surveys have him in first

That pact could also hurt Warren, who's also to the left of the moderate Biden and Klobuchar.

'Our campaign is on the rise,' said Tim Hogan, Klobuchar's communications director. 'We've never made caucus deals with other campaigns and don't intend to.'

The Times initially reported that Biden officials, led by the campaign's Iowa director Jake Braun, made an overture to Klobuchar strategist Pete Giangreco at a Des Moines restaurant this week suggesting that their supporters caucus for the other candidate at sites where Biden or Klobuchar don't get the needed 15 per cent support in order to gain delegates.

The Democratic Iowa caucuses are unique.

Caucus-goers gather at sites all around the state.

During the first vote, participants go stand with the candidate they support.

If they don't account for 15 per cent of those at the caucus site, they must throw their support to another candidate who met that 15 per cent threshold.

Republicans also hold Iowa caucus meetings, but candidates win based on a straight vote.

Former South Bend Mayor Pete Buttigieg now comes in third place in Iowa. He's the only candidate to have briefly hop-scotched the frontrunner, former Vice President Joe Biden, in Monmouth polling

Sen. Elizabeth Warren is registering at 15 per cent in the new Monmouth survey. The threshhold for viability in the Iowa caucuses is 15 per cent. If a candidate's supporters don't make up this number, they have to toss their support to a viable option

Biden would likely get more out of an alliance than Klobuchar, as he's historically polled above 15 per cent and she hasn't.

The Monmouth survey has had Biden in frontrunner status since polling started in April, except for a brief period in November when Buttigieg scooted ahead.

Other Iowa surveys, however, have shown Sanders out front.

Monmouth has had the Vermont senator climbing slowly over the past six months.

In April, Sanders recieved 16 per cent of the vote share.

That dipped down to 8 per cent in August - and since then he's moved up 13 points.

The Iowa caucuses take place Monday.