You probably do. There are only a handful of states -- Ohio, Florida, Virginia, Wisconson . . perhaps a couple of others -- where politically aware people must really swallow hard and vote for the "lesser of two evils"(LOTE). For the rest of us -- I'm speaking to and for politically aware people! -- our vote doesn't matter; it will have no effect on who the next president is.
Politically aware people in CA, NY, IL, MD, WA, MN, MA, CT-- also in TX, OK, UT, WY, and others -- already know thattheir state is going to go for Obama -- or for Romney.Their vote will have no effect in determining the next president.
So take advantage of this "impotence"! Use your vote to express your abhorrence of the Disgusting Duopoly. You may do so safely, so do it!
Example: I live in Maryland. Current polls show Obama preferred by 60% of voters; 36% like Romney. What a wonderful thing it would be, to cut down Obama's vote to 55%, with Jill Stein getting 5%.
Another example: Texas. There Romney is preferred by 58%, Obama by 39%. There it would be great if Romney got 53% of the vote, Gary Johnson getting 5%.
Politically aware people, whether liberal or conservative, should, in most states, vote their true preferences, rather than got the LOTE route. In most states they can safely do so.
If FreeVote-ism should catch on, we in the United States would have a chance, over several presidential cycles, to claw back out of the miasma into which our politics have sunk.
[ If you are unsure whether you have a Free Vote, a great site to check is electoral-vote.com. Polling results, by state, are up-dated daily. The site has a map, where states where one candidate is preferred over another by more than 10 percentage points are colored either Deep Blue, or Bright Red. ]