Did the McCain voters who delivered Ind. to Clinton break law?

The short answer is yes in most cases. (Only voters who planned to both vote for McCain in the general and a majority of Dems in other races, or who had voted for a majority of Dems in the previous election, would be in compliance.)

There's no real good way to enforce the law, however. And that's a good thing. I don't want my government knowing for whom I voted.

But the point here is that Americans have a civic duty -- especially when it comes to the democratic process -- to do their very best to follow the law, whether or not they run the risk of being punished.