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WASHINGTON — Republican presidential hopeful Mitt Romney essentially ties Barack Obama in the nation's key battlegrounds, a USA TODAY/Gallup Swing States survey finds, while rival Newt Gingrich now trails the president by a decisive 14 percentage points.

That reflects a significant decline by the former House speaker since early December, when he led Obama by three points.

The poll of the dozen states likely to determine the outcome of November's election addresses the electability argument that has driven many Republicans: Which GOP contender has the best chance of denying Obama a second term?

In a head-to-head race, Romney leads Obama by a statistically insignificant percentage point, 48 percent to 47, the survey finds.

But Obama leads Gingrich, 54 percent to 40 percent. The president's standing against him has risen nine points since early December; Gingrich has fallen by eight.

Gingrich fares less well than Texas Rep. Ron Paul, who trails Obama by seven points, 50 percent to 43 percent, and former Pennsylvania senator Rick Santorum, who also trails by seven points, 51-44.