The U.S. Supreme Court agreed Friday to take up an issue that could change a key element of the system America uses to elect its president, with a decision likely in the spring just as the campaign heats up, NBC News reported.

The answer to the question could be a decisive one: are the electors who cast the actual Electoral College ballots for president and vice-president required to follow the results of the popular vote in their states? Or are they free to vote as they wish?

A decision that they are free agents could give a single elector, or a small group of them, the power to decide the outcome of a presidential election if the popular vote results in an apparent Electoral College tie or is close.

America has never chosen its president by direct popular vote. Instead, when voters go to the polls in November, they actually vote for a slate of electors chosen by the political parties of the presidential candidates. Those electors then meet in December, after the November election, to cast their ballots, which are counted before a joint session of Congress in January.

The cases before the Supreme Court involve faithless electors during the 2016 presidential election. Instead of voting for Hillary Clinton, who won the popular vote in Colorado, Micheal Baca cast his vote for John Kasich, the former Republican governor of Ohio. And in Washington state, where Clinton also won the popular vote, three of the state's 12 electors voted for Colin Powell, the former secretary of state, instead of Clinton.

Read the full story on NBCNews.com.