Majority of Americans think there should be a third party

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The idea of a third centrist party is always one with superficial appeal, but falls apart upon execution in most countries (the world must be littered with the remains of parties bursting into action promising "politics based on practicality"). I can think of two main examples of big tent centrists in politics:

The sprawling pudding-like "natural party of government" type, full of careerists and hacks (Fianna Fail, Canadian Liberals, the Institutional Revolutionary Party, the Independence party of Iceland and so many more). 

The smaller centrist parties exist primarily to act as a magnet for floating votes and underepresnted groups (the obvious and most pathetic example is the Australian Democrats; but the Lib Dems and D66 count as well). Unfortunately, the party exists as an outlet for the permanently dissatisfied; and typically crater when ever the party starts doing "serious stuff". These include any artificial attempts to start centrism as a viable strategy, and lack the pretension and deep roots of the previous group.

To be honest, I don't think either variety can work in America. Although I think third parties are not totally doomed by the election system - I can count a few handful that have popped up over the years, centrism is not viable in a country where less and less people are truly "centrist". People may think politicians are too polarised, but they are wrong. The electorate is polarised. The parties are streamlining because that is the pressure from voters.

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OK, I'll accept Kansas because Orman is promising the same kind of bland centrism that is popular with these things (Kansas is in a funny place right now though, and hardly representative of the rest of America).

As for the rest - all those states you mentioned becoming toss-ups prove my point. They aren't becoming toss-ups because half of fervent GOP's woke up one day and thought "huh, maybe I should vote for Obama". It's because of demographic changes. American politics is less and less about convincing people you are right, and more about catering to those who know you're right.