Romney hopes for a convincing win
Republican Mitt Romney is hoping for a big victory in the New Hampshire presidential primary as he seeks to build momentum ahead of a crucial, but tougher, state contest later this month.
His rivals fought for a strong second-place showing as Mr Romney, the former governor of neighbouring Massachusetts, is well known to voters in New Hampshire where he owns a holiday home, and was expected to win. But the margin of victory could determine whether he quickly clinches the Republican nomination for president or faces a gruelling battle in South Carolina on January 21 and in the primary race overall.
Mr Romney just won last week's Iowa's caucuses, the first contest in the race to select a challenger to Democratic President Barack Obama in the November election.
Given Mr Romney's lead, the focus is largely on the wide-open contest for second place, with Rick Santorum, Ron Paul, Newt Gingrich and Jon Huntsman in contention.
With voting under way, Mr Gingrich said he believes "the biggest story today" is that Mr Romney will fall short of "any reasonable expectation" in New Hampshire, particularly since he has been heavily favoured there all along.
The Republican establishment has largely rallied behind Mr Romney, hoping to avoid a long, divisive primary fight that could undermine prospects of defeating Mr Obama, whose popularity has fallen because of the slow US economic recovery. A narrow win in the nation's first presidential primary - or a surprisingly strong finish from one of his rivals - will be played up as more evidence that Republicans still have their doubts about Mr Romney.
A strong showing in New Hampshire could galvanise the anti-Romney vote ahead of the South Carolina vote. The conservative state has a strong track record of picking the eventual Republican nominee, and Mr Romney is seen as too moderate and, therefore, vulnerable there.
But recent polls show him leading against a split field. A win in South Carolina, following victories in Iowa and, likely, New Hampshire, could make his nomination seem inevitable.
None of Mr Romney's rivals has proved to be a consistent and credible threat to him so far. The latest to emerge from the pack to challenge Romney is Mr Santorum, the former Pennsylvania senator who used a passion for social conservatism and a populist economic message to come within eight votes of Mr Romney in Iowa's caucuses.
In New Hampshire, "second place would be a dream come true," Mr Santorum said as he raced through a campaign schedule that spanned more than 14 hours.