Also, in a primary, I would say always to vote your conscience, even if your favorite candidate is clearly not going to win, since, as you mention, the more delegates your candidate wins the bigger role s/he can play in the convention. (For a general election of course this calculus doesn’t hold, since the non-winners have no bargaining power after the election, thus if you have a preference between the front runners you are better off voting that preference rather than a third-party candidate. I bet most of the people who voted for Nader in 2000 wish they could take back their votes…).