Ron Paul has been denied a speaking slot at the convention because he refuses to endorse Romney, saying "That would undo everything I’ve done in the last 30 years. I don’t fully endorse him for president."
I don't envy the decision libertarians must make in the next few months. Libertarian Party candidate Gary Johnson will likely be on the ballot in all 50 states, offering an alternative to those who can't hold their noses and vote for Romney. With as close as the race may well be, a few thousand votes for Romney or Johnson could decide the election.