First, why Walker?
1. He's a governor, and Dear Leader's leap from the Senate aside, from Jimmy Carter on, previous executive experience (counting Poppy Bush as Veep) has been the normal White House route. That rules out Ted Cruz, Marco Rubio, and Rand Paul, as well as, possibly, Jeb Bush as an ex-governor too long removed from office. Chris Christie probably is too liberal. John Kasich will probably stay out. Rick Perry
2. He's shown the chops as a union-buster.
3. By winning a recall, and re-election, he's shown he's a winner.
That said, Ed Kilgore notes the Koch Corleones are likely to do the equivalent of a "request for proposals" before officially tapping one candidate. And Vox says that the Kochs might not tap anybody too quickly, lest they lose leverage — as risible as it is to imagine a group of billionaire brothers losing political leverage.
Meanwhile, the first point may be worth bearing for Democrats, too. Martin O'Malley's a (recently ex)-governor. Hillz Clinton was the executive power behind the throne for the Slickster, and after running for Senate, then was an executive of sorts as Secretary of State. Bernie Sanders, whatever his odds are, is a senator. (So is Elizabeth Warren, should she change her mind; that said, her short Senate tenure would put her in the Obama category.
Now, that said, the joking header?
The David H. Koch Fund for Science is a major supporter of PBS' Nova science program. (Nova's already been criticized for pulling its punches on climate change ever since getting Koch money, and PBS in general has been accused of kowtowing.) Hence my joking about the science of Wisconsin cheddar!