In the crowded Republican presidential race, Trump with 31 per cent was way ahead of Florida Senator Marco Rubio, with 15 per cent of prospective Republican primary goers, CNN said.
Three other candidates Senator Ted Cruz from Texas (13 per cent), Ohio Governor John Kasich (11 per cent) and former Florida Governor Jeb Bush (10 per cent) were running neck-to-neck for the third position.
In the two-way Democratic party race, Sanders (54 per cent) has a 14-point advantage over former Secretary of State Hillary Clinton (40 per cent), CNN said.
Since 1952, New Hampshire primary has been considered a major testing ground for Republican and Democratic nominees.
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Candidates who perform badly drop out of the race and those who do well become strong contender for their party's nomination.
Unlike other American states, where only registered party members can vote for their candidates, in New Hampshire independents or non-registered peoples have the option to vote in the primary elections of both the parties.