The Wall Street Journal:

Oklahoma Governor Mary Fallin is starting to feel surrounded. On her state’s southern border, Texas has no income tax. Now two of its other neighbors, Missouri and Kansas, are considering plans to cut and eventually abolish their income taxes. “Oklahoma doesn’t want to end up an income-tax sandwich,” she quips.
On Monday she announced her new tax plan, which calls for lowering the state income-tax rate to 3.5% next year from 5.25%, and an ambition to phase out the income tax over 10 years. “We’re going to have the most pro-growth tax system in the region,” she says.