Hillary Clinton has tons of cash, but she can’t shake off Bernie Sanders.Donald Trump keeps threatening to spend his own money, but he hasn’t had to use much of it. He’s leading the Republican field, feasting on free media coverage, while spending a fraction of what his rivals, and super PACs promoting them, have spent. If his rivals hadn’t been able raise large sums the GOP race would probably be over—Mr. Trump’s celebrity, name recognition and charisma would already have carried the day.

Apparently oblivious to the failure of “big money” to dictate the race, the goo-goos—the good-government crowd—have cranked up the same theme they use every election year. “We must,” they say, “have campaign finance reform.” We must “get money out of politics.” The Supreme Court must reverse its 2010 decision in Citizens United and allow “reasonable” regulation of campaign finance.

But what would “reasonable” regulation actually look like? Well, we have an idea, because once, not that long ago, Congress passed “reasonable” regulation.

Saturday marks the 40th anniversary of one of the most momentous Supreme Court decisions: Buckley v. Valeo. In Buckley, the Supreme Court struck down provisions of the Federal Election Campaign Act that threatened core First Amendment freedoms. The 1976 decision is as important to democracy as 1954’s Brown v. Board of Education is to education and civil rights. Its anniversary is a time for reflection on what might lie ahead if “reformers” get their way.

Many Americans vaguely favor “campaign finance reform.” It is only when such reform gets specific that people realize—often too late—that they themselves are the targets of that reform.