Why must it be either a Democratic or Republican candidate? This seems to be a major weakness in American politics, that a failure with one party leads to people endorsing the other, regardless of their positions and merit. I know it is easier said than done, but it looks like there is room for more parties.
While I agree with you that it would be great to have a viable third party in the United States, the very structure of the voting system here (the single member district plurality system) has been shown to favor a two party system under various game theory analyses.
Check out Duverger's law for more insight on this:
I live in a country (Canada) that falls under the article's counterexamples. We have four parties in Parliament. None of them can break out of the 30s, currently, in terms of their polling numbers. In addition, no party has actually won a majority in 6 or 7 years.
