It would require a constitutional amendment. The Electoral College is established in the Constitution -- right there in Article II -- and that means that to abolish, or alter it in any way requires, 1) a two-thirds majority in the House and Senate, 2) three-quarters of the states to ratify the change within a seven-year window.
The idea is that doing it this way people living in smaller, often more rural states, would get their voices heard too. If the U.S. had elections based on popular votes alone, the candidates would focus most of their attention on areas with large populations. Would it be fair that policies benefitting California or New York, where a big chunk of Americans lives, should be the main ones enacted, at the expense of policies that would focus, let’s say, on the Rust Belt states, who were key in deciding the last presidential election?
On the flip side, the Electoral College creates a situation where candidates focus their attention mostly in a small number of “battleground” states instead of the whole country. Case in point - Hillary Clinton’s campaign.
Hillary Clinton didn’t even visit Wisconsin.
Even if the ideological separation weren't so large, the Electoral College and the constitutional amendment process are both designed to empower small states. The 12 largest states in the country combine for more than half the population, but the other 38 states could amend the Constitution as they pleased without them.
Small states love the Electoral College because it gives their voters an outsized influence. In Wyoming, there are 188,000 people per electoral vote. In California, it's 739,000. Sure, politicians would rather get California's electoral votes, but the power of a single voter is a lot higher in Wyoming.
And as California drifts farther away ideologically from the rest of the country, the Electoral College keeps the state's liberal ambitions for the rest of the country in check. Ditching the Electoral College would allow California to impose imperial rule on a colonial America. Small states know this, and they're not going to let it happen anytime soon.
http://www.washingtonexaminer.com/the-electoral-college-isnt-going-anywhere/article/2608884
http://www.cnn.com/2017/09/14/politics/electoral-college/index.html
http://bigthink.com/paul-ratner/why-the-electoral-college-exists-and-not-going-anywhere