WASHINGTON – The Supreme Court has upheld a requirement that forces groups to say who is paying for issue advertising directed at candidates in an approaching election.

The justices on Monday affirmed a lower court decision in a case involving ads that mention candidates but don’t call for the election or defeat of one.

The case involved a Colorado think tank called the Independence Institute and ads that it wanted to run in 2014 that mentioned Colorado Democratic senators Mark Udall and Michael Bennet. Udall lost his 2014 re-election bid, while Bennet won a second term in 2016. The Independence Institute said it wanted to run a similar spot in 2016.

The group objected to revealing the names of its largest contributors. Senate Majority Leader Mitch McConnell, R-Ky., supported the group’s Supreme Court bid.

The Supreme Court has generally upheld disclosure requirements even as it has struck down limits on raising and spending money in political campaigns.

Justice Anthony Kennedy cited the importance of disclosure in his majority opinion in the Citizens United case in 2010 that freed corporations and labor unions to spend freely in elections, as long as they did so independently of candidates.

Kennedy wrote that “the public has an interest in knowing who is speaking about a candidate shortly before an election.”

The case is Independence Institute v. Federal Election Commission, 16-743.