Jonathan Bernstein endorses party-line voting. His reasoning:
But in the usual cases, voting the party line will be the best option. Think that makes the vote seem almost meaningless? You’re right: Voting never is enough. Which is the other reason to join, and be loyal to, a political party. By doing so, one can be ready to really work for change in the political system by working for change within the party. Granted, straight-ticket voting isn’t technically necessary for one to become involved in party affairs, but it fits the general idea of how to go about being an effective political actor.
The Dish 