If Clinton had squeaked it out, she sure as heck wouldn't have had a "mandate" either.

Clinton's entire popular vote margin can be found in California alone.

Because the popular vote does not elect the President, the entire campaign strategy is built around not wasting time or money in lopsided states that a candidate has zero chance to win. California is such a one party state that many districts did not even have a Republican listed in down ballot elections. Since their vote would not count and since there was nobody else to vote for in other elections, conservatives stay home in such states. Liberals may do the same in places like Alabama..but California massively outnumbers Alabama.

There is no telling what the popular vote might be if the President was actually elected by that method and campaign strategy depended on it.