Hillary Clinton’s once commanding national lead over Bernie Sanders 'has largely melted away'

A new poll shows that younger Democrats prefer Mr Sanders by a ratio of two-to-one

Bernie Sanders and Hillary Clinton looking like BFFs. (Joe Raedle/Getty)

The once convincing lead enjoyed by presidential hopeful Hillary Clinton over her nearest Democratic challenger has all but disappeared, according to a new poll published just weeks away from the first voting.

Bernie Sanders has closed the gap with Ms Clinton to with seven points, with 48 per cent of Democratic primary voters across the country supporting her while, and 41 per cent backing the Vermont Senator.

Mr Sanders' support is particularly strong among younger voters, according to the latest New York Times/CBS News poll. Voters under the age of 45 favour Mr Sanders over Ms Clinton by roughly a roughly 2-to-1 ratio, the newspaper reported.

Hillary Clinton is relying on Bill’s charisma and his abilities as a fundraiser (Getty)

The closing of the gap, barely three weeks before primary voters in Iowa – technically it is a caucus rather than a ballot - cast the first votes in the 2016 presidential race, does not mean all is doomed for Ms Clinton.

The same poll found that seven out of ten Democratic voters, including most supporters of Mr Sanders, still believe Ms. Clinton will ultimately win the party’s nomination, the newspaper reported.

Voters expressed deeper confidence in her ability to be an effective commander in chief and more of her supporters say their minds are made up compared with Mr Sanders’s backers.

Previous contests have seen candidates rise and fall in the weeks before the first votes are cast, and national polls at this stage of the race are not necessarily predictive of the final outcome of the months long nominating battle.

U.S. Democratic presidential candidate Bernie Sanders speaks at a campaign rally at the Iowa State Fairgrounds (Reuters)

But Mr Sanders’s surge has clearly unnerved the Clinton campaign, and she has responded aggressively. On Tuesday, Ms Clinton’s daughter, Chelsea, launched an attack on Mr Sanders.

Until now, Chelsea Clinton has shied away from directly naming Mr Sanders in her speeches. But campaigning in New Hampshire she focussed on the senator when asked by a young voter how to excite young Americans, who have indicated their support for him.

“I never thought that I would be arguing about the Affordable Care Act or Obamacare in the Democratic primary,” she said, at an event in Manchester.

“Senator Sanders wants to dismantle Obamacare, dismantle the CHIP programme, dismantle Medicare and private insurance.”

The candidate has herself sharpened her attacks on Mr Sanders, as more than one poll puts him ahead of her in the crucial state of Iowa.

Speaking at an event in Ames, Iowa, where Ms Clinton was endorsed by the Brady Campaign, a group that has campaigned vigorously for gun control, Ms Clinton claimed Mr Sanders had a weak voting record on this issue and that he had supported the pro-gun National Rifle Association (NRA), a powerful lobby group.

“You [Bernie Sanders] voted for what the NRA said was the biggest NRA priority giving them immunity, and he says, 'Well, I’m from Vermont',” she said, according to the Associated Press.

“Pat Leahy, the other senator from Vermont, voted against immunity for the gun lobby, so no, that’s not an explanation.”