It takes a lot of work to get on the ballot, in the first place (especially for third party candidates). Even when someone does, people tend to vote *against* their last choice, rather than *for* their first choice, because of the winner-take-all style of our voting system. Changes like ranked-choice voting would go a long way to helping with the latter problem, at least.
Here’s the underlying problem: the ballot, which was once the property of voters organically organizing themselves into parties, has become the property of state legislatures dominated by the two major parties. The introduction of uniform, printed state ballots—a reform of the late 1800s intended to quash the buying and selling of individual votes—also gave legislatures the power to determine who was qualified to be on the ballot. Republican and Democrat-controlled legislatures swiftly learned that they could use this power to smother rising third parties like the Populist Party, and gave themselves automatic lines on the ballot while instituting onerous petitioning requirements to hinder other upstarts. (When political scientists argue that the first-past-the-post system of awarding representation invariably forces voters into a two-party duopoly, they forget to note that it’s only when ballot lines are so rigidly guarded that two specific parties, in this case the Ds and the Rs, manage to artificially lock themselves in power.)
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The hard reality is that if we ever get a major new political party, it won’t be built by think tank denizens. It will be built first in states like New York, Connecticut, and Oregon, where minor parties don’t have to risk “spoiling” the election because they can endorse candidates from another party, or cities like Minneapolis and San Francisco where ranked-choice voting (where you can assign your vote to a series of candidates in order of preference) eliminates that barrier. And then it will move to power in a few states and maybe a few congressional seats. The presidency will be its final prize, not its first.