The former governor of New Mexico is about to win the Libertarian Party nomination. Libertarianism is an extreme ideology, when taken seriously. But Gary Johnson seems to be to libertarianism what François Hollande is to socialism: in the direction but within the mainstream. In fact, looking over his policy positions, the only place where he seems to step outside political norms was an offhand call to eliminate Medicare Part D.
He also seems to be a bit nutty on monetary policy, but that is within Republican norms.
Whether any of this will get him past 15% in the polls (needed to be on the debate stage) or 5% in the popular vote (needed for federal funds) is beyond me. And I have no idea if his presence will swing any particular states, the way the Libertarian candidate may have swung the Virginia gubernatorial race in 2013.