By LAWRENCE LESSIG

CAMBRIDGE, Mass. — FOR the first time in modern history, the leading issue concerning voters in the upcoming presidential election, according to a recent Wall Street Journal/NBC News poll, is that “wealthy individuals and corporations will have too much influence over who wins.” Five years after the Supreme Court gave corporations and unions the right to spend unlimited amounts in political campaigns, voters have had enough.

Republican candidates, including Chris Christie, Ted Cruz and Lindsey Graham, and the main Democratic candidates, Hillary Rodham Clinton, Martin O’Malley and Bernie Sanders, all acknowledge the problem, with some tying it to the Supreme Court’s 2010 decision in Citizens United, which unleashed virtually unlimited “independent” political spending.

The solution proposed by some, notably Mrs. Clinton, Mr. Graham and Mr. Sanders, is amending the Constitution.

It sounds appealing, but anyone who’s serious about reform should not buy it. For a presidential candidate, constitutional reform is fake reform. And no candidate who talks exclusively about amending the Constitution can be considered a credible reformer.

This is not because we don’t need constitutional reform. Of course we do. No sane constitutional designer would have picked the mix of restrictions and rights that our Constitution has been read to embrace. And with due respect to the Supreme Court, neither did our framers. Amendments will be essential to restoring this democracy, just as a healthy diet is essential to the recovery of a patient who has suffered a heart attack.

Nor is this because a constitutional amendment is impossible. No doubt it is ridiculously difficult to amend our Constitution. The veto of one house in just 13 states — representing as little as 5 percent of the American public — could block an amendment. But in the last hundred years we’ve added 10 amendments to our Constitution, with an average ratification time (excepting the most recent, which took 202 years) of less than 16 months. We’ve done it before; we can do it again.

Nor does this mean that the many reform organizations pushing for a constitutional amendment are not themselves true reformers. Of course they are, and their work is the most important force building the essential political movement that real reform will require.

But even if we could pass amendment to reverse Citizens United soon (and not since the Civil War has an amendment been adopted with support from just one party), it would not solve the problem of money’s influence in American politics.

If the core problem is politicians beholden to their funders, then giving Congress the power to limit the amount spent or the amount contributed would not resolve it. Regardless of how much was spent, the private funding of public campaigns, even with limits, would inevitably reproduce the world we have now.

Real reform will require changing the way campaigns are funded — moving from large-dollar private funding to small-dollar public funding.

Democrats, for example, have pushed for small-dollar public funding through matching systems, like New York City’s. Under a plan by Representative John Sarbanes, Democrat of Maryland, contributions could be matched up to nine to one, for candidates who agree to accept only small donations.

Republicans, too, are increasingly calling for small-dollar funding systems. The legal scholar Richard W. Painter, a former “ethics czar” for President George W. Bush, has proposed a $200 tax rebate to fund small-dollar campaigns. Likewise, Jim Rubens, a candidate in the Republican primary for Senate in New Hampshire last year, proposed a $50 tax rebate to fund congressional campaigns.

Either approach would radically increase the number of funders in campaigns, in that way reducing the concentration of large funders that especially typifies congressional and senatorial campaigns right now.

Some 13 states already offer two kinds of public campaign funding: In Arizona, Connecticut and Maine, “clean elections” laws offer full subsidies to candidates who agree to limit their spending and private fund-raising, while Florida and Hawaii match small donations up to a certain amount. The Brennan Center for Justice wants to expand New York City’s matching-contribution law to the rest of the state, saying it would increase transparency, accountability and voter turnout.

Most Americans are deeply skeptical of reform, and especially reform that costs money. So it’s much easier to call for a constitutional amendment than to propose public financing.

But solving the crisis in our democracy will not be cheap or easy. We won’t end the corruption of a system beholden to the funders until we, the citizens, are the funders. That truth takes courage to utter. This election needs that courage.