"Governor Romney has very strong positions on enforcing immigration laws and lowering taxes. Mike Huckabee has a very weak and troubling record on both of those issues," Madden said. McCain has a "pro-amnesty approach on immigration" and voted against tax relief that spurred the economy, he said.
Romney, also a former chief executive of the management consulting firm Bain & Company, has already been facing scrutiny and questions over his Mormon faith.
His latest troubles came as campaigning wrapped up for the Christmas holiday and less than two weeks before January 3, when voters in Iowa begin the state-by-state contests to choose Republican and Democratic nominees for the November 2008 presidential election.
New Hampshire voters go to the polls in a primary election five days later, on January 8.
HUCKABEE SURGE
The turn of events - especially the surge in popularity among conservative Christian voters by Huckabee, a former Southern Baptist preacher - threatened to upend Romney's strategy for winning the Republican nomination.
Romney always trailed Republican front-runner Rudy Giuliani, a 63-year-old former New York mayor, in national opinion polls.
Romney's strategy for mounting a challenge rested on winning the conservative early voting states, where support for the more centrist Giuliani was weak, in hopes of building momentum and support nationwide.
Until the past month, that strategy had paid off and Romney was seen as the favourite in Iowa and New Hampshire, especially among conservative Christians. But Huckabee has gained increasing support with his folksy populism and quick wit.
A Reuters/Zogby poll showed Huckabee within 1 percentage point of Romney in Iowa last week, a result echoed by other surveys. A Boston Globe poll released on Sunday found McCain within 3 percentage points of Romney in New Hampshire.
