I do the same thing. If I think that an election won't be close, I vote for the Republican, since I don't want to help split the conservaitve vote, helping the Democrat win with less than the majority. If I think that the Republican candidate is too liberal and that the election won't be close, I vote for the Constitution Party candidate, and, if that party doesn't have a candidate, in that race, I vote for the Libertarian. In Oct. 2004, I thought that Bush was too liberal and that Kerry would win 57% of the vote in my state, Illinois. I voted for the Constitution Party candidate, and Kerry won 57% in IL.
I wish that more conservatives would vote the way that we do. It might cause Republicans to become more conservative.
The two party system is so overrated.