U.S. Democratic and Republican presidential candidates are campaigning hard with their messages to New Hampshire voters on Monday, just 24 hours ahead of the state's critical primary ballot.

A new poll indicated freshman Illinois Senator Barack Obama opening a wide lead in the battleground state over fellow Democratic Senator Hillary Rodham Clinton, while the Republican race remained a statistical dead heat.

Obama, riding a surge from his surprise victory over Clinton and Edwards in last week's Iowa caucus, is aiming to secure support among younger voters who delivered for him in the previous ballot, as well as among independent voters expected to participate in New Hampshire's primary, said Dean Lacy, a government professor at Dartmouth College.

A new poll suggests Democratic presidential candidate Barack Obama, seen here speaking at a campaign rally on Friday in Portsmouth, N.H., is pulling ahead of Senator Hillary Rodham Clinton in the state.
(M. Spencer Green/Associated Press)

"Obama supporters have been out in droves" canvassing support in the state to combat the well-funded and organized team Clinton has established in New Hampshire in the preceding months, Lacy told CBC News in an interview Monday from the state.

Nearly half of New Hampshire's voters are neither registered Republicans nor Democrats, the CBC's Neil MacDonald said.

On Sunday, fire marshals had to shut the doors and bar waves of supporters flocking to Obama's events, as he strives to become the first black president in U.S. history.

Clinton sought to revive her campaign by casting her rival Obama as an inexperienced candidate long on rhetoric, but short on substance.

Clinton praised Obama on Monday as "a very talented politician," but added she was the only candidate who has proven over the past few months that she can handle the intense pressure placed upon the party's front-runner.

"If he's going to be competing for president — and especially to get the Democratic nomination and go up against whomever the Republicans put up — I think it is really time to start comparing and contrasting him as I have been scrutinized for all of this year," Clinton told CBS's The Early Show.

McCain takes aim at Romney 

Meanwhile, among the Republican fold, polls showed veteran Arizona Senator John McCain neck and neck with Mitt Romney, who enjoys a high profile in the state as the former governor of the neighbouring state of Massachusetts.

Republican presidential hopeful Senator John McCain addresses supporters during a campaign stop in Nashua, N.H., on Monday. A new poll shows McCain has pulled even with former Massachusetts governor Mitt Romney among New Hampshire voters.
(Charles Dharapak/Associated Press)

McCain, however, won the New Hampshire primary in 2000 over the eventual Republican victor, President George W. Bush, and is viewed as highly popular in the "Live Free or Die" state for his often maverick positions during his long Senate career.

McCain's once-fledgling campaign has undergone a dramatic resurgence since observers all but wrote off the former navy pilot and Vietnam veteran's chances earlier this year.

"Tomorrow is the day when we will tell the world that New Hampshire again has chosen the next president of the United States," McCain told a couple of hundred sign-toting supporters on Monday, joking "vote early and often."

Romney, with his "Washington is broken" message, is desperate to avoid being shut out in the larger contests following his defeat in Iowa, despite picking up some delegates by winning the Wyoming caucus last week.

"He's [Romney's] the front-runner, but John McCain has caught up with him," Lacy told CBC News.

Former Arkansas governor Mike Huckabee, who upset Romney in the Iowa vote despite Romney's spending spree on advertising ahead of the vote, was trailing in third, according to polls. 

"If we come in anywhere in the third and fourth slot, we're going to do great. I'd like to do better than that, but you have people who have had a lot more money spent here," Huckabee told CNN on Monday.

The former Baptist minister's relatively low support likely stemmed from not being able to draw from a broad base of evangelical Christians, as he did in last week's caucus victory, Lacy said.

According to the new USA Today/Gallup poll, Obama had 41 per cent support, up from 32 per cent in mid-December. Clinton was at 28 per cent, down from 32 per cent, while former North Carolina senator John Edwards had 19 per cent.

New Mexico Gov. Bill Richardson had six per cent, and no other Democratic candidate had more than three per cent.

On the Republican side, McCain had 34 per cent, up from 27 per cent in mid-December, while Romney had 30 per cent, down from 34 per cent. Huckabee held 13 per cent, while Rep. Ron Paul of Texas and former New York mayor Rudy Giuliani were tied at eight per cent.

No other Republican candidate, including former Tennessee senator and well-known actor Fred Thompson, who conceded Sunday he was focusing on South Carolina rather than New Hampshire, was above three per cent.

Both surveys had a margin of error of 4.4 percentage points, a small enough gap to consider the Republican race tied.

With files from the Associated Press