I have in the past voted for Libertarians not because they have a chance of winning, and not simply to "send a message."
My votes for independent or 3rd party candidates increases the chance that their party will be able to appear on the next state-wide ballot without have to meet the onorous and steep cost Democrats and Republican avoid by writing ballot "access" laws to benefit themselves.
It also increases the chance, however slightly, that an out-of-step-with-the-mainstream idea might get some discussion during an election, which will influence the future of the existing maor parties. Without the votes in earlier elections for Populists and Socialists, the Democratic Party of today would be very, very different and Republicans would legislate and govern quite differently than they do. The votes for the various incarnations of the Progressive Party have permanently altered both parties. Republicans (across the board) and Democrats (particularly in local offices) freely borrow ideas that Libertarians champion.
Regularly in many local elections, both partisan and "non-partisan," only one of the major parties actually fields a candidate, while a Libertarian, Green, or other party may appear on the ballot. Once in California I proudly voted (for a non-partisan office) for the Peace and Freedom Party candidate (whom, given her stance on issues, I usually describe as "a Communist") rather than the completely looney left-wing, but famously-named (so of course she would win), Democratic Party candidate. And I didn't have to hold my nose at all on that one.
So I disagree with those who declare such votes "wasted."
For the Republic, Steven