However, frontrunner Mr. Romney was not having a clear field. His numbers have tumbled in recent days as the focus has shifted to his fortune and his tax returns.

Mr. Romney, with an estimated fortune of US$250-million, revealed during a debate Monday that he pays 15% tax — because he is taxed on his investments.

Republicans and Democrats have also demanded that he release his tax returns as his usual for candidates running for president. Mr. Romney has promised to release them in April when, he said, he becomes the official nominee.

However, ABC News reported that Mr. Romney has US$8-million invested in 12 funds listed on a Cayman Islands registry. Another investment, said to be worth between US$5-million and $25-million, was “domiciled” in the Cayman Islands.

The revelations will add to his image — as put forward by his opponents — as an out-of-touch multi-millionaire and corporate raider.