1. Can he raise the money it takes to run a national campaign? Because of the recall election, Walker ran three times in four years, and built a national base of donors in the process. Or did he? Some of those donors may have fervently wanted him to win his fight against the Democrats and public-sector unions, but would also prefer other Republicans for president.

2. To what extent will Walker run on a policy agenda, and what will that agenda be? His national reputation is tied to his position on labor law. He could use that to run as a union-buster, or he could use it to run as someone who wants government to work for taxpayers and not for its own employees. If he chooses the latter course, he’ll need a broader agenda to illustrate the theme. Similarly, he faces a choice between trying to appeal to middle-class voters based on his biography alone — unlike the last few Republican nominees, he isn’t a rich guy — or based on policies that benefit those voters.

3. Can he keep his fans as he goes national? As governor, Walker has mostly been able to stay out of national debates. Take immigration. His current supporters include hard-line foes of amnesty for unauthorized immigrants as well as people who think the party needs to soften its position. Can he find a way to take a stand without alienating one side or the other? And how disillusioned will conservatives be when they find out the compromises that Walker, like any governor, has made?