That would be Mitt Romney, supported for the GOP nomination by 21 percent of Republicans and Republican-leaning independents. That’s double the support of his closest potential rival, but it also leaves 79 percent who prefer one of 13 other possible candidates tested, or none of them.

When Romney is excluded from the race, his supporters scatter, adding no clarity to the GOP free-for-all. In that scenario former Florida Gov. Jeb Bush, former Arkansas Gov. Mike Huckabee and Kentucky Sen. Rand Paul have 12 or 13 percent support from leaned Republicans who are registered to vote. All others have support in the single digits.

Were Romney to run again, he’d likely face some of the same challenges that dragged out the 2012 GOP contest. He’s supported by only half as many “strong” conservatives as those who are “somewhat” conservative, 15 vs. 30 percent in this poll, produced for ABC by Langer Research Associates.