It is a truism of politics that even if there isn't a candidate that you want to vote for, there's surely someone that you would vote against.
The problem with this is that it presumes that the 'other' candidate is at least acceptable; what isn't usually taken into consideration with that saying is what to do when one is less than impressed with EITHER of the mainstream candidates.
The most obvious solution is to simply continue to apply the principle by voting for neither of them. The value of this option becomes even more significant when the two main political parties have become so polarized, so entrenched, so dominant that they skew and bias the political scene so thoroughly that alternative candidates are marginalized and excluded -- effectively denying the voting public the free exercise of the franchise.
I would suggest that it is well past the time for the voting public to make it known that they do not appreciate what the election process has devolved to, that they do not like being limited to just one or two candidates from the two main political parties, and that they do NOT want the current process to limit them to just a couple of 'mainstream' parties.
Personally, I'm more than a little disgusted with the way political campaigns have become a blood sport, the general malaise most people have about the process, the political pandering, and being obliged to vote for what I consider the lesser of two evils. I, like most people, am disgusted with the whole process and resulting jackassery. What used to be sarcastic comments on the state of politics have become entirely too true: "The opposite of 'pro' is 'con', so the opposite of Progress is Congress", "Politicks comes from the Latin 'poly', meaning many; and 'ticks', a species of blood-sucking parasites", "No one's life, liberty, or property are safe while the Legislature is in session", "Giving money and power to Government is like giving whiskey and car keys to teenage boys", and so on. Think about the other, similar, sayings that you know -- and whether or not you think they're more true now than they were in years past.
If you are less than impressed with the political process, or you aren't entirely committed to voting for one of the main candidates, then I would encourage you to join me in sending a message to those that are supposed to be our public servants: that it's nigh time they cleaned up their act, started working WITH each other instead of at cross purposes, and started making it possible for us to have the kind of government that we want, DOING what we want: vote for anybody but either of the two mainstream candidates -- hell, vote for Ralph Nader, or Ron Paul, if that's what it takes. Hell, write in Adolf Hitler, if that's what it takes to make it painfully clear that you're not voting for either of the other two. If you don't have a 3rd-party alternive in a particular race, then vote for whoever the challenger is for an office. Voting for Nader or someone else might sound risky ("But what if he actually gets elected!"), but it isn't, really: there are undoubtedly enough people still going to vote Republicrat or Demolican that Nader (or whoever) getting into office is unlikely in the extreme. What voting for him WILL do, however, is let the other parties know that there is a significant portion of the voting public that is less than pleased with them -- and that's the point that needs to be made.