Donald Trump and Ted Cruz have led polls since early December, and their leads over Marco Rubio and Ben Carson have grown. But there’s still time for the race to shift. At this point in 2012, the winner of the Republican caucuses in Iowa, Rick Santorum, was polling sixth.
Iowa has voted for the eventual nominee in only two of the last six Republican nomination fights that did not involve an incumbent president. Mr. Rubio and Chris Christie are vying to emerge as the leading establishment alternative and gain momentum headed into New Hampshire.
Donald Trump has led polls by a wide margin for months, following a trajectory similar to the 2012 winner, Mitt Romney. At this point in 2008, John McCain had already started his comeback that would overtake Mr. Romney in the polls.