If we had a pure popular vote system, as many people who are disappointed with the 2016 outcome are now proposing, it would not be feasible—because of third party candidates—to ensure that any candidate would win a popular majority. Even in 2016, for example, although Hillary Clinton won the popular vote, she only received a plurality (48 percent)—not a majority; third party candidates took the rest.
If we abandoned the Electoral College, and adopted a system in which a person could win the presidency with only a plurality of the popular votes we would be swamped with candidates. Every group with an ideological or major policy interest would field a candidate, hoping that their candidate would win a plurality and become the president.
There would candidates of the pro-life and pro-choice parties; free trade and anti-trade parties; pro-immigration and anti-immigration parties; and parties favoring or opposing gun control—just to use the hot issues of today as examples.
We see this effect in parliamentary systems, where the party with the most votes after an election has to put together a coalition of many parties in order to create a governing majority in the Parliament. Unless we were to scrap the constitutional system we have today and adopt a parliamentary structure, we could easily end up with a president elected with only 20 percent-25 percent of the vote.