WaPo:
Reviewing the presidential election results, many commentators note that Donald Trump — like several previous Republican presidential candidates — prevailed in the electoral college without winning the popular vote. This is true, but it’s also irrelevant. It’s irrelevant legally, of course, because the Constitution provides for the election of a president through the electoral college. But it’s also irrelevant in terms of the democratic legitimacy of the result.
In the election concluded Tuesday, Hillary Clinton received more popular votes than Trump. This does not mean, however, that Clinton would necessarily have prevailed in an election that was determined solely by the popular vote. This is because the popular vote total is itself a product of the electoral college system. As a consequence, we do not know what the result would have been under a popular vote system, let alone whether Clinton would have prevailed.
The reason for this is because the electoral college system encourages the campaigns (and their surrogates and allies) to concentrate their efforts on swing states — those states in which the electoral votes are up for grabs — at the expense of those states in which one party or the other has no meaningful chance to prevail. The presidential campaigns make no meaningful effort to turn out votes in populous, but non-competitive states such as California, New York and Texas. There is no advantage to running up the score in a state that is solidly in one camp, nor is there much benefit in trying to drive up turnout in pursuit of a hopeless cause.