Scott Walker is the only ambidextrous candidate in the Republican field. He appeals equally to the Republican establishment and the Tea Party/evangelical wingers.
All other candidates fit neatly in one or the other box. While Jeb Bush's record in Florida used to make him the most attractive member of his family to conservatives, he has blown that accolade with his strong support for immigration amnesty and Common Core.
Chris Christie was never the darling of conservatives, but his appeal to establishment Republicans is obvious.
Neither Bush nor Christie is a switch-hitter.
On the right, Ted Cruz's views fit the Tea Party like a glove but his brand of fiery politics may be too much for establishment ears. He is so effective and so on target that he scares the cautious GOP establishment to death. Mike Huckabee and Rick Santorum have perfect pitch in appealing to evangelicals, but, perforce, are too out there for the more establishment types.
Rand Paul and Marco Rubio both have the potential to be transcendent, Paul because he is blazing new ideological grounds and Rubio because of his cautious, respectful tone.
But both are very young and the establishment doesn't want to take chances. Can Rubio hold his own on a national stage (without frequent gulps of water)? Can Paul's libertarian ideology catch on? The establishment would rather not find out with the presidency on the line.
Paul also runs afoul of the national security wing of the establishment, a potent part of the centrist coalition.
Rick Perry once spanned the centrist and Tea Party wings of the party until he imploded in 2012. Can he recover from his ungraceful exit last time? Can he overcome the phony indictment under which partisan Texas prosecutors have forced him to labor? We don't know yet.
Cruz, Paul, Rubio, Huckabee, Santorum and Perry are all are hoping to be crossovers, keeping their Tea Party base but appealing to the center as well. But Walker is effortlessly able to battle for the establishment, the Tea Party and the evangelical vote. And there is no reason for him to have trouble with national security voters, either.
The Wisconsin governor has been elected and reelected, and defeated a recall attempt in a key swing state. His combat credentials are enough to assuage worries the establishment might have about a first-time candidate. His record on job creation and fiscal discipline is admirable. He is the Christie who succeeded; Wisconsin is where the New Jersey governor dreamed his state would be.
Yet Walker's credentials as a battler against the left earn him backing from the right wing of the Republican Party, including his stand against municipal unions, amnesty and Common Core.
From the Republican point of view, he is America's most successful governor. He offers a chance to take the education issue away from Hillary Clinton. He has actually turned a school system around, ironically, by applying some of the very same remedies Clinton first proposed in Arkansas in 1982 but has long since abandoned in her sycophancy toward the National Education Association and the American Federation of Teachers.
And Walker has been vetted. He has been through a trial by fire that no other GOP presidential aspirant has. Under the constant pressure of the municipal labor unions, continuously tested in recalls (both his own and his senators'), he has survived nicely.
Energetic, young, charismatic and fresh, Walker provides just the kind of generational contrast Clinton has most to fear. And, now with Mitt Romney out of the race, he can spread his wings.