A bizarre moment when Joe Biden playfully bit on his wife Jill's finger as she waved in his direction before a crowd has been caught on camera.

The presidential hopeful was appearing at the start of his eight-day 'No Malarkey' bus tour of Iowa on Saturday.

Biden and his wife were on stage at a rally in Council Bluffs as she introduced him at the first stop of the tour.

As she flung her arm in his direction to make a point, Biden dodged the wave. But when she motioned a second time, he decided to have a taste of one of her fingers, getting a laugh out of her and a crowd of supporters.

It was welcome comedy relief for the Democratic hopeful, who is out projecting confidence as he ignores his many Democratic presidential competitors and pledges that he will unseat President Donald Trump in 2020.

Joe Biden dodges the first time his wife Jill waves in his direction at the start of his eight-day 'No Malarkey' bus tour of Iowa on Saturday in Council Bluff

On the second wave, however, Biden playfully nibbled on his wife's finger

The much-needed comedy relief was well received by Biden's spouse and the crowd

The former vice president has pledged to win the February 3 Iowa caucuses, despite recent polls suggesting his standing there has slipped in recent months.

'I promise you, I promise you', Biden told a few hundred supporters outside his campaign office in Council Bluff, 'we´re going to win this race, and we´re going to beat Donald Trump, and we´re going to change America'.

His tour bus - which will cover 800 miles in Iowa - had the words 'No Malarkey' emblazoned across the side.

Behind the optimism, Biden aides acknowledge he must sharpen his message and bolster his voter outreach operation ahead of the caucuses that start Democrats´ 2020 voting.

But his advisers also insist he has wide support and remains well-positioned to recover any lost ground.

His chief argument - his perceived strength against Trump - was on clear display Saturday.

Sidestepping his philosophical tussle with progressive senators Elizabeth Warren and Bernie Sanders over the party´s direction, Biden struck a general-election posture.

He added an emphasis on small town and rural America, an electoral swath where Democrats have struggled in recent elections but that could prove critical in both the nominating fight and November battlegrounds.

'We´re going to touch on what we think is a forgotten part of this campaign', Biden said, bemoaning the effects of Trump´s tariffs on Iowa farmers and highlighting his own rural policy plans shaped with the help of former Iowa Governor Tom Vilsack.

The former Obama agriculture secretary recently gave Biden his most high-profile Iowa endorsement.

His wife followed suit in Council Bluffs, introducing her husband as the 'only candidate who can take on Trump in places like Florida and Wisconsin and Pennsylvania and Michigan'.

Iowa polls suggest that Biden, while a front-runner nationally, is in a jumble near the top. Mayor Pete Buttigieg, 37, of South Bend, Indiana, appears to hold a narrow edge over Biden, 77; Warren, 70; and Sanders, 78.

The senators have animated the party´s left flank, while Buttigieg joins Biden in Democrats´ center-left wing but is calling for generational change.

The former vice president has pledged to win the February 3 Iowa caucuses, despite recent polls suggesting his standing there has slipped in recent months

Mayor Pete Buttigieg, 37, of South Bend, Indiana, appears to hold a narrow edge over Biden (pictured Saturday in Iowa), 77; Warren, 70; and Sanders, 78. in Iowa

Biden aides reject any framing of the bus tour as a reset; they see it as a way to drive home his potential strengths with Democratic voters consistently citing Trump´s defeat as their top priority, even beyond the particulars of intraparty debates on issues like universal health care.

'As people get closer and closer to February, they become more and more practical about this', Vilsack said ahead of Biden´s trip. 'He can make the strongest case ... that he is in a position to get things done, and he is in a position to win'.

Biden takes a selfie with supporters following a campaign stop in Council Bluffs, Iowa, Saturday

Thus far, Buttigieg, Warren and Sanders have drawn consistently larger Iowa crowds than Biden, while some party activists criticize his campaign as insufficiently aggressive.

'In terms of people out there knocking on doors, who attend other campaign events, district events, I can't name a member of the southeast Iowa Democrats who's supporting Joe Biden', said Glenn Hurst, a leader of Iowa Democrats´ Rural Caucus.

Biden greets members of his audience following a campaign stop in Council Bluffs, Iowa

Bobbie Moore, a party volunteer and Biden supporters who came to see him Saturday, stopped short of criticizing the campaign. But she noted the crowd 'isn´t one-10th of what was here for Pete' Buttigieg just days ago.

Fairly or not, Biden´s national staff has fueled skeptical assessments with pronouncements that he doesn't have to win Iowa to win the nomination. Iowa is overwhelmingly white; Biden´s national advantage leans heavily on nonwhite voters who will help determine outcomes in Nevada, South Carolina and many March 3 Super Tuesday states.

Yet all the hand wringing misses key variables in Iowa, Vilsack and other Biden backers contend. They argue his support is wider demographically and geographically than other leading candidates. They point to rural areas and Iowa´s growing minority population that, while small, could prove important with many candidates dividing the overall caucus vote.

Moore, 70, said Biden is a 'known quantity' whose support isn't as obvious as Buttigieg and others.

Another Biden volunteer, Phyllis Hughes Ewing, said outside media underappreciated Biden´s appeal. 'I´m on the phones with voters two nights a week for several hours at a pop', she said. 'I´m a boot on the ground... and everyone has good things to say about Joe'.

The bullishness leans heavily on the way caucus votes are counted.

The Biden team is laser-focused on the viability threshold requiring candidates to get 15 per cent support in a given precinct to have votes counted toward delegates.

Biden´s team believes he´ll be viable in every one of the 1,679 precincts on caucus night, a reach other leading candidates may not match.

Then, they believe Biden will be a top beneficiary of 'realignment' - subsequent ballots that allow voters who supported a nonviable candidate to choose another who´s still standing.

Biden is reflected in a cell phone camera as he grasps the hand of a supporter in Iowa

That process could be a double boost for Biden, their theory goes. First, top contenders like Warren or Buttigieg whose support might be anchored in more liberal cities and suburbs would get no practical benefit from first-ballot votes in more rural precincts where they fall short of 15 per cent.

Second, several of the lower-tier candidates running as moderates - Minnesota Senator Amy Klobuchar, for example - could fall short of viability across much of the state. Biden advisers confirmed they already are mapping out realignment ballot strategy.

They´re also looking to organized labor for help. Biden won the endorsement of the International Association of Fire Fighters at the outset of his campaign, and the organization already has tapped its locals across the state to canvass. Biden´s second stop Saturday was a local fire station.

For minority outreach, the campaign recently hired state Representative Ras Smith, a member of the Iowa Legislature´s Black Caucus, and it has more than a dozen bilingual organizers, including deputy political director Claudia Chavez, focusing on Latino voters.

But beyond all the particulars, Biden´s fundamental argument returns to political pragmatism.

Harold Schaitberger, the firefighters´ national union president, compared the dynamics to 2004, another primary fight when Democrats were desperate to oust a Republican president.

Howard Dean led in Iowa for much of 2003, wowing progressives and drawing large crowds. Massachusetts Senator John Kerry ultimately came back to win the caucus and nomination, though he lost to President George W. Bush in the fall.

Schaitberger, whose union backed Kerry, smiled as he recalled a newspaper headline from late 2003: 'Kerry dead in the water'.