Jonathan Martin writes in the New York Times that the campaigns of Walker and Bush (disclosure) already reflect different general-election strategies:

[Bush] is telling Republicans, in effect, that they must accept a changing country: that the path to the presidency will be found through appealing to voters who may not look like them, and with a standard-bearer whose state and immediate family resemble tomorrow’s America. . . .
The party’s way forward, by Mr. Walker’s lights, lies in demonstrating toughness in the face of intense opposition from the left and mobilizing those who are already inclined to support conservatism. . . .
Applied to the electoral map, the inside route would most likely mean that Mr. Walker would try to capture a band of Midwestern and Great Lakes states filled with the sort of working-class white voters he reflects. He frequently notes that Republicans have not carried Wisconsin since 1984, a not-so-subtle suggestion that he could. He also would surely eye four other Rust Belt states President Obama carried both times: Iowa, Michigan, Ohio and Pennsylvania.
Mr. Bush would almost certainly set his sights on the increasingly diverse states Mr. Obama carried at least once in his two elections: Colorado, Florida, Nevada, New Mexico, North Carolina and Virginia. The voting-age population in each of those states is at least 25 percent nonwhite, and in some of them substantially higher.

Walker’s “inside route,” assuming it’s actually his strategy, would involve carrying more states that have consistently voted Democratic. All of the states Martin lists as Bush targets voted for George W. Bush in 2004. Wisconsin, Minnesota, Michigan, and Pennsylvania did not.

Florida was the state where Obama won by the smallest margin in 2012. Next was Ohio, then Virginia, and — neck and neck — Colorado and Pennsylvania. Add the first three states and either of the last two to the Republicans’ total, and they win an electoral majority. If Republicans did better evenly across the country, that is, it would mean taking a little from column A and a little from column B.