Republican Santorum catches Romney in U.S. polls

By Lily Kuo

WASHINGTON (Reuters) - Former U.S. Senator Rick Santorum has surged into a virtual tie in opinion polls with Republican presidential front-runner Mitt Romney, setting up a tough fight in the party's primary in Michigan on Feb 28.

Picking up support from voters aligned with the conservative Tea Party movement and white Christian evangelicals, Santorum rose rapidly to edge 2 percentage points ahead of Romney in a national poll released by the Pew Research Center on Monday.

Santorum, a social conservative, also came within 2 points of Romney in a national Gallup poll, and was ahead by 15 points in Michigan, where Romney was born and has been expected to do well.

"It's a real threat to the kind of sense of inevitability that Romney was trying to project a few short weeks ago," said Christopher Arterton, a professor at George Washington University.

The Republican candidates are engaged in a state-by-state battle for their party's nomination to challenge Democratic President Barack Obama in the November 6 presidential election.

Conservative voters wary of the more moderate Romney may be coalescing around Santorum, who appears to be benefiting from fights between Republicans and Democrats over abortion, gay marriage and contraception in recent weeks.

Almost twice as many Tea Party supporters and white evangelical Christians in the Pew poll chose Santorum over the former Massachusetts governor.

That survey had Santorum with 30 percent support from Republican and Republican-leaning voters, compared to 28 percent who preferred Romney.

The Gallup poll put Romney at 32 percent and Santorum at 30 percent. Newt Gingrich, who led the field as recently as late January, was in third place with 16 percent.

The Public Policy Polling poll result in Michigan is probably most worrying for Romney, whose father was governor of the state in the 1960s.

Santorum led Romney by 38 percent to 23 percent in the Midwestern state, which holds its primary in two weeks.

Arizona also holds its primary on February 28, and Romney is favored to win, but Michigan is the real battleground for the two front-runners who are campaigning there this week.

Santorum swept Republican nominating contests in Missouri, Minnesota, and Colorado last week - his first victories since being announced the winner of the Iowa caucuses in January - and has since closed a wide lead Romney held over him.

Data for Monday's Gallup poll was based on telephone interviews from February 8 through Sunday of 1,162 registered Republican and Republican-leaning voters. The margin of error was plus or minus 4 percentage points.

The Pew poll was based on telephone interviews from February 8 through Sunday of 552 registered Republican and Republican-leaning voters. The margin of error was 5 percentage points.

(Editing by Doina Chiacu)