Newt Gingrich, who is fighting to slow the momentum of Mitt Romney towards securing the Republican presidential nomination, received a big boost at the weekend as a Las Vegas casino tycoon pledged $5m (£3.2m) towards an independent group that is supporting his run.

Media reports said the source of the much-needed funding was Sheldon Adelson, a billionaire casino magnate and a long-time donor to Republican candidates. Mr Adelson – a strong supporter of Israel, as is Mr Gingrich – has pledged to give another $5m to whoever wins the Republican nomination.

The first cheque will be written to a group called Winning our Future, a so-called super-political action committees, or PAC, that was formed to help Mr Gingrich win the nomination.

In yesterday's debate, Mr Gingrich lashed out at Mr Romney for allowing the main PAC supporting him, Restore Our Future, to air attack ads that helped knock Mr Gingrich off the top spot in last week's Iowa caucuses.

The new funds are timely, with Mr Romney appearing vulnerable in South Carolina, the next state with a primary election.

Airing across the state starting today will be a TV commercial harshly attacking Mr Romney as the co-founder of Bain Capital, a venture capital firm that specialised in turning around companies and thus, often, laying off workers.