WASHINGTON (AP) — The Supreme Court has ruled unanimously Monday that states can require presidential electors to back their states’ popular vote winner in the Electoral College. The court reviewed a case involving so-called “faithless electors” in Washington state and Colorado.

In Washington’s case, four presidential electors voted for candidates other than Hillary Clinton, who won the state’s popular vote in 2016. The state fined the electors $1,000, prompting a court battle.

The ruling comes just under four months before the 2020 election, leaving in place laws in 32 states and the District of Columbia that bind electors to vote for their states’ popular-vote winner. Electors almost always do so anyway.

So-called faithless electors have not been critical to the outcome of a presidential election, but that could change in a race decided by just a few electoral votes.