Ironically, that's precisely what Trump thought was going to happen, and it's why he kept saying he might not accept the results of the election if he didn't win.
To clarify, what you describe has now happened four times. EVERY time, it was the Republican who lost the popular vote, but won the EC vote. Given the population distribution in the U.S., it will only ever be.
It is essentially a mathematical impossibility for the Democratic nominee to win the EC vote and lose the popular vote. It's actually how the Electoral College was designed to work.