KEENE/NASHUA, NEW HAMPSHIRE (REUTERS) - Bernie Sanders and Pete Buttigieg sought on Monday (Feb 10) to build on their strength as front runners as an energised Senator Amy Klobuchar gained ground in an up-for-grabs race the day before New Hampshire votes in its Democratic presidential primary.

Mr Buttigieg and Mr Sanders, who emerged first and second in delegates in the opening nominating contest in Iowa last week, face eight rivals in Tuesday's vote. But Ms Klobuchar pulled into third place in two opinion polls.

The man they are seeking to take on in the November election, Republican President Donald Trump, held his own raucous rally on Monday night in Manchester, New Hampshire, in a move to distract from the Democratic nominating contest.

The large number of Democratic candidates and undecided voters makes the outcome of the New Hampshire contest unpredictable, said Mr Ray Buckley, chairman of the state Democratic Party.

"This is anyone's race to win," he told reporters on Tuesday. "That makes these final hours even more exciting."

One undecided voter, 65-year-old Stacy Sand, showed up to see US Senator Elizabeth Warren but remained torn between her and Ms Klobuchar. "I might just be deciding as I head into the polls," she said.

'DECISION TIME'

Mr Sanders, 78, a progressive who represents neighbouring Vermont in the US Senate, has long led in opinion polls in New Hampshire. But Mr Buttigieg, a 38-year-old moderate and military veteran who served two terms as mayor of South Bend, Indiana, has picked up ground since Iowa.

In Plymouth, Mr Buttigieg tried to reach out to undecided voters, referring to "future former Republicans" who he said were more than welcome to back his campaign.

"It's decision time," he said. He took a shot at Mr Sanders, saying that the self-described democratic socialist would have a hard time pulling in moderate voters.

"Knowing how much depends on bringing Americans together, we cannot risk alienating Americans at this critical moment," he said. "And that's where I part ways with my friend Senator Sanders."

In a separate event, Mr Sanders aimed his attacks at Mr Trump. "I know not everybody agrees with everything I say, but I think what we can agree about is that we cannot continue having a president who is a pathological liar," he told a crowd at a sports club in Manchester.

On Monday night, Mr Sanders draw a large crowd in Durham, where US Representative Alexandria Ocasio-Cortez, a progressive star, and rock band The Strokes joined him for a rally.

'LONG TIME COMING'

A pair of polls released late on Sunday and early on Monday showed Ms Klobuchar pulling into third place behind Mr Sanders and Mr Buttigieg following the party's debate in New Hampshire last Friday.

"We feel the surge, for me it's been a long time coming,"said Ms Klobuchar, a moderate from Minnesota, noting she had visited New Hampshire 23 times since she entered the presidential race a year ago.

She told a crowd of more than 200 at Keene State College that she was the candidate who could appeal to independents and Republicans disenchanted with Mr Trump's divisive policies and rhetoric.

"There are a bunch of moderate Republicans and independents out there who feel this and know just what I'm talking about," she said. "You need a candidate with big coattails who brings people with her."

Although she criticised Mr Buttigieg in last Friday night's debate, Ms Klobuchar refrained from mentioning any of her rivals on the campaign trail, sticking to her promise to unite the country, lower drug prices, improve infrastructure and increase funding for treatment of drug addiction and mental health issues.

A Boston Globe poll, conducted with Suffolk University and WBZ-TV, showed Mr Sanders with 27 per cent, Mr Buttigieg with 19 per cent and Ms Klobuchar with 14 per cent among 500 likely voters polled over the weekend in New Hampshire. The survey had a margin of error of plus or minus four percentage points.

A separate poll by WHDH/Emerson College also showed Ms Klobuchar pulling into third.

Ms Klobuchar rose after former vice-president Joe Biden, a fellow moderate, stumbled in Iowa and showed an uneven performance in New Hampshire, where he called a voter on Sunday "a lying dog-faced pony soldier", making a joke with phrasing adapted from John Wayne movies.

'IT COMES TO YOU'

Ms Warren, aiming for a stronger-than-anticipated finish in a state neighbouring her home state of Massachusetts, kept her focus on the President, declining to criticise her Democratic rivals or to draw sharp contrasts between their policies.

"It comes to you, New Hampshire, to decide, when there's this much fear, when there is this much on the line, do we crouch down, do we cower, do we back up, or do we fight back?" she said to a standing ovation in Portsmouth.

Mr Biden, coming off a disappointing fourth-place finish in Iowa and trailing in New Hampshire polls, likewise focused on Mr Trump.

"Trump is going to tell us over and over again the economy is on the ballot this year," Mr Biden told a crowd of fewer than 100 people in Gilford, adding that the President was benefiting from economic policies put in place by his Democratic predecessor, Mr Barack Obama, and did not deserve credit for America's robust economy. Mr Biden was Mr Obama's vice-president.

Support for Mr Biden, the one-time Democratic front runner tumbled nationally after the Iowa contest by five points to 17 per cent, behind Mr Sanders' 20 per cent, according to a Reuters/Ipsos poll released on Monday.