New Hampshire goes to the polls in crucial US vote

New Hampshire heads to the polls on Tuesday in the crucial first US presidential primary with Donald Trump pledging to bounce back and Hillary Clinton looking to narrow the gap on Bernie Sanders.

The small northeastern state, home to just 1.3 million, is the battleground that could shake out a crowded Republican field of candidates, pitting Trump and arch-conservative senator Ted Cruz against more establishment candidates led by senator Marco Rubio.

The high number of registered independents, who can choose to vote either Democrat or Republican, and the up to 30 per cent of undecided voters in the final days mean everything is in play.

Snow fell heavily in the state late on Monday, snarling traffic and creating a last-minute obstacle for voters and candidates who braved plunging temperatures and freezing winds.

“This is crunch time,” the Republican frontrunner Trump told thousands of cheering supporters at an event delayed slightly by snow in Manchester.

“You have to go out, you have to vote, we have to celebrate tomorrow evening,” he said. “Let’s have a big, big victory.”

Trump has energised broad swaths of blue collar and generally less educated Americans, angry about economic difficulties and frustrated at what they see as their country losing its stature in the world.