The firebrand junior senator from Texas is backed by 31 percent of those likely to attend the Republican caucuses that start the presidential nomination season on Feb. 1. Trump is a distant second at 21 percent, up slightly from 19 percent in October, but below his peak of 23 percent in August.

Cruz’s 21-percentage-point jump since October is the largest surge between Iowa Polls recorded in at least the last five presidential caucus campaigns. When first and second choices are combined, he has the support of 51 percent of likely caucus-goers. The senator’s great leap forward comes largely at the expense of Carson, as Iowa’s evangelicals appear to have picked the candidate they want to get behind. The retired neurosurgeon, now barely in third-place, is supported by 13 percent, down from the first-place showing he posted in October, when he was at 28 percent.