WASHINGTON - Republican presidential hopeful Mitt Romney holds a double-digit lead over the rest of the field in new national polls released Thursday.

Coming off his primary wins in Arizona and Michigan Tuesday night, the former Massachusetts governor has jumped to a 16-point lead over Rick Santorum in the battle for the Republican presidential nomination, according to the latest Rasmussen poll.

The survey, conducted Feb 29, has Romney at 40 percent support among likely Republican primary voters. Santorum, the former Pennsylvania senator, came in a distant second at 24 percent.

This is Romney's biggest lead to date and the highest level of support any GOP candidate has earned in regular surveying of the race, according to Rasmussen. Two weeks ago, it was Santorum 39 percent, Romney 27 percent.

Former House Speaker Newt Gingrich earns 16 percent support, closely followed by Texas Congressman Ron Paul at 12 percent.

In a separate poll by Gallup, Romney also enjoys solid lead over the rest of the field. Thirty-five percent of Republican voters back Romney as their party's nominee, 11 points ahead of Santorum at 24 percent, according to the latest Gallup five-day rolling average. Gingrich ranks third at 15 percent, and Paul at 11 percent.

Riding strong performances in GOP caucuses in Colorado and Minnesota and a non-binding primary in Missouri on Feb 7, Santorum had seen his poll numbers skyrocketing, at some point holding a double-digit lead over Romney in major national polls.

But the former senator failed to maintain the momentum running into the pair of primaries Tuesday due to disappointing debate performances and his positions on some social issues considered out-of-mainstream.