On big races (larger than city council races) there is one point to remember -- you as an individual will never cast the deciding ballot! Hence there is no reason to vote for the lesser evil. I find it ironic that we hear the "wasted vote" argument most in precisely the races where it applies least.
A Presidential race will never be decided by one vote. And if, by some mathematical chance it got that close, it would be decided politically in the courts, in the legislature or in Cook County, Illinois (where I plan to be buried so I can continue to vote after I'm dead and gone).
I tell people that if you go to the polls to cast the deciding ballot in major races and if you value your life, you are making an irrational decision. The chances of dying enroute in a car, plane or meteor accident are far greater than the chance of casting the deciding ballot.
We as individuals don't vote to select the winner. As a practical matter we vote to tell everyone else which choice best represents the direction which we want the country to go. Hence voting lesser evil sends the wrong message. Remember, if we keep voting the way we have been voting, we will keep getting what we have been getting.
Even if once in your life you missed the chance to cast that mythical deciding ballot, the harm from selecting the wrong person in one election is more than offset by a lifetime of giving voter support to the lesser of two evils rather than standing up for what you believe.
The history of third parties in America is that they serve as the vanguard for new ideas. If they start to draw votes, one or both of the two big parties steal their ideas (that is the one item we welcome them to steal from us). The most successful third party in the 20th century was the Socialist Party. First the Democrats and then later the Republicans piecemeal adopted just about every major tenet of the 1916 Socialist Party platform.
We are the opposite of the Socialists, but we find their success instructive. The radical ideas about liberty that we started with in 1971 are now being seriously debated or, in some cases, implemented by the other parties. An increasing number of Libertarian votes is indeed noted by the politicians as well as the media.
So rather than waste your vote on Demopublicans, cast a meaningful ballot that clearly says what you believe. Cast a vote for bigtime government downsizing. Cast a vote for freedom. It's time to vote Libertarian.