White House hopeful Rick Santorum has opened an eight-point lead over presumptive frontrunner Mitt Romney among likely Republican voters nationwide, a new poll showed Sunday.

Thirty-six percent of those surveyed said they supported the Christian conservative, while 28 percent said they preferred the former Massachusetts governor, according to the latest results from Gallup's daily tracking poll.

Less than a week ago, Romney was leading Santorum, a former US senator from Pennsylvania, by two points, putting the two candidates in a statistical tie.

Former House speaker Newt Gingrich trails the two leaders with 13 percent, while veteran libertarian Texas congressman Ron Paul was not far behind with 11 percent, the poll showed.

Santorum -- who surprised Romney with wins in nominating contests earlier this month in Missouri, Minnesota and Colorado -- is now trying to maintain his momentum for the February 28 primary in Michigan, Romney's home turf.

The Gallup poll was conducted from Tuesday through Saturday among about 1,200 likely Republican voters. The margin of error is plus or minus four percentage points.

In late August the Republicans will confirm their candidate to face Democrat Barack Obama in the November 6 presidential election.