Without further ado, our first no. 1 ranking goes to:
1. Jeb Bush
Bush's December announcement that he plans to "actively explore" a run for the presidency shook up the GOP primary. First, major GOP donors have already started flocking to him, a development that could squeeze potential rivals. Second, the move made it clear how serious the son and brother of presidents is about running after years of rumors that he would ultimately seek another office once his term as Florida governor had ended.
Bush has serious strengths, including the support of donors from New York to Florida to Texas. But he's also got critical weaknesses with the conservative base on policy issues such as Common Core that could be important in the primary. By being the first Republican out of the gate, he is giving himself the opportunity to attract as much of the establishment as he can to his side. If he can't do that, Bush may not end up running at all. But, right now, he could be the best-positioned GOP candidate by a hair.
2. Marco Rubio
The senator from Florida has the highest upside of anyone on this list. His combination of biography, demographic profile, and rhetorical skill had convinced many Republicans in the wake of his 2010 Senate victory that he was the future of the Republican Party. He still could be. Rubio has assembled a top-notch political team and is planning a major media blitz in mid-January to promote his new book, American Dreams. These would seem to be surefire signs of an imminent presidential campaign. But Rubio's future suddenly looks uncertain now that Bush has entered the race and is threatening to suck Florida's donor community dry.
We're still betting that Rubio will jump in. He's too talented—and too ambitious—to pass up a race that could define the GOP for a generation. Still, a Rubio run isn't the sure thing we thought it would be a few months ago. And although we think he's the candidate with the most potential if he does run, the sudden doubt over whether he will bumps him to No. 2 for now.
3. Rand Paul
Paul has cemented himself as one of the most intriguing GOP figures in America. He's also almost certainly running in 2016, having hired advisers in early-primary states and gathered his team for a strategy summit in November. Paul enters 2015 with an enviable floor of support—both financial and in the polls—that he inherited from his father's two runs. And he's been systematically trying to expand his appeal, from the Chamber of Commerce to Jewish leaders, while also presenting himself as a new kind of Republican who can win over disaffected Democrats and independents. Still, a Paul nomination would mark a sharp departure, especially on foreign policy, for the GOP, and that may be a bridge too far for the traditionalist party.
4. Scott Walker
Walker checks virtually every box in a Republican primary: He has executive experience, boasts a fiscally conservative record as governor, is conservative on social issues, and became a right-wing favorite by fighting organized labor in his first term. Moreover, Walker may be unique in his ability to appeal to both the activist and establishment wings of the GOP.