If you're a Republican living in California, why bother to vote in this presidential election? The state is already sewn up for Barack Obama -- he'll get all 55 electoral votes and your ballot won't mean diddly.

Answer: Same reason Democrats living in Texas (where 38 electoral votes are in the bag for Mitt Romney) and throughout in the South (112, depending on how one counts, most for Romney) should vote today. The overall U.S. vote matters, even if it may not seem like it as those TV pundits begin assigning red and blue to the nation's political map tonight.

The presidential candidate who wins both the popular vote and the all-important Electoral College tally brings a mandate to the White House that he wouldn't have in the case of a split. Perceptions of legitimacy matter. Might some voters pay so much attention to those Electoral College handicappers that they choose to stay home, thinking their votes will be meaningless? No doubt. And could that have a dire effect in states where the vote is expected to be close? Absolutely. Low turnout, whether its cause is apathy, defeatism or voter suppression, could affect the outcome.

Californians of all political persuasions have plenty of other reasons to vote, of course. The state ballot is replete with highly consequential propositions, including two tax initiatives that have been pitched as public-school bailouts. Efforts to sway the electorate with shadowy out-of-state money have been remarkable, and not in a good way. There's that much at stake. Fortunately, apathy does not appear to be a concern this election. Republicans and Democrats alike indicate that they're highly motivated. Equally so, it turns out. And that's appropriate in an election that, as the polls open today, looks to be astoundingly tight.

We hear it every four years: Every vote counts. This time, perhaps more than ever, that's the truth.