As a result, candidates find themselves caught in an arms race: trying to raise enough money to compete, in contributions of $2,700 or less (far more than any middle-class family can spare), often facing opponents funding their own campaigns or incumbents with established fund-raising machines or outside money. There’s a natural pressure to find a way out of that trap, using whatever technique your lawyers and consultants cook up. That’s why every politician who has support from large donors now has a supportive super PAC.

And there will always be a way out. The problem is not the Supreme Court — it’s the First Amendment itself. The challenge in regulating campaign spending is not deciding whether money is speech or corporations have rights, it’s defining the boundaries of the election. Elections are a special zone, and by regulating spending clearly intended to influence the election, we keep it a zone of political fairness, where voters hear all sides and elected officials can remain independent. (Think of it like the signs limiting electioneering within 75 feet of the polling place.)

The provisions challenged in Citizens United and the earlier cases all dealt with the question, “What makes an ad an election ad?” Before 2002, the principle was that it had to have “magic words” like “vote for.” McCain-Feingold tried to establish that broadcast ads that mentioned a candidate 30 days before a primary or 60 days before an election would be considered campaign ads (“electioneering communication”). That’s what brought Citizens United, the organization, and its movie attacking Hillary Clinton, to the attention of the Federal Election Commission in 2008.

But what about speech that mentions candidates long before an election? Or ads that don’t mention a candidate at all? For example, groups funded by the Koch family ran ads in the congressional elections of 2014 attacking “Obamacare” without ever mentioning a congressional candidate by name. When party and ideology are as tightly aligned as they are, an ad doesn’t need to connect all the dots to push a voter who dislikes President Obama’s health insurance program to vote Republican or an environmental activist to vote Democratic. But this kind of robust open debate about public issues is exactly what the First Amendment is intended to protect.

Then there are all the other ways that the wealthy influence policy, without getting involved in elections — through media, lobbying and philanthropy. Each channel is legitimate and most efforts to restrict them would create more problems than they solved. What Mr. Sanders calls “the billionaire class” will not lose its influence even after all the court decisions back to 1976 have been reversed.

It may be futile to try to restrict the influence of the very wealthy, but we can offset it by opening the system up and making it easier for a candidate to run and be heard, or for people working together to put a new idea on the agenda. Both Democratic presidential candidates have called for some kind of system of public financing that matches small donations, along the lines of New York City’s program, which matches small contributions six to one. Every current citywide elected official participated in the system, and small donors, including the match, accounted for 61 percent of the money spent in the 2013 elections.