Kansas Gov. Sam Brownback has put the state on what he calls a "glide path to zero" income tax. But that glide path is far from being clear or smooth.

On the face of it, Brownback seems to enjoy a remarkably strong political position. He's a conservative Republican, flanked by GOP supermajorities in both legislative chambers. His allies helped purge moderate Republicans from the state Senate in last year's election.

"I think the road is open," Brownback says. "I think we do provide an alternative model. I think we do provide a red-state model."

In 2012, Kansas eliminated the state income tax for about 190,000 small businesses and cut the rate substantially for high-income individuals.