The man hoping to lead Republican presidential hopeful Rick Santorum to victory previously worked for a politician known for his "antisemitic, racist and anti-immigrant views".

Mr Santorum's campaign manager is Michael Biundo, who was one of the key figures in Pat Buchanan's ultimately unsuccessful presidential bid in 1996.

Mr Buchanan, a bombastic right-winger popular with social conservatives, has been described by the Anti-Defamation League on several occasions as racist and antisemitic and an "unrepentant bigot".

According to a report published by the hate monitor in 2009; "Buchanan has repeatedly demonised Jews and minorities and has openly affiliated with white supremacists. He has also claimed that the sovereignty of the United States is being undermined by Israeli control." He no longer has a political role but is a political analyst for television news channel MSNBC.

The ADL noted recently that Mr Buchanan's activities "demonstrate an increasing embrace of extremist causes.

"In fact, Buchanan's online forum was home to several statements promoting Holocaust denial before it was taken down due to media exposure," said the ADL. "The growing antisemitism and bigotry behind Buchanan's mainstream façade is cause for renewed concern."

Mr Biundo served as Mr Buchanan's deputy campaign manager in the 2006 New Hampshire primary, a race in which he beat the eventual Republican nominee Bob Dole.

Mr Santorum, a devout Catholic, was the shock success story of the Iowa caucus earlier this month, but was unable to follow this in the New Hampshire primary.

He is expected to regain support in the more conservative South Carolina, which holds its primary this Saturday. With the almost certain departure of the only other moderate - Jon Huntsman - from the race, most analysts expect Mitt Romney to secure the Republican Party's nomination and take on President Obama next November.