[ubernostrum]

Imagine telling a Republican "hey, how would you like all those rural Republicans in California to have their vote actually count for once?" Right now there's close to no point for a CA Republican to vote for president, because the state's going for the Democrat no matter what they do. Same is true for many states which go for Democrats: outside of the major cities they have significant Republican populations, who are aware their votes don't matter but suddenly would under a popular-vote system.