As a measure of democracy, one of the more encouraging statistics of the 2016 presidential race is the fact that the average contribution to the long-shot campaign of Senator Bernie Sanders is $31.30. It would be hard to buy any politician for $31.30. That is exactly the message Mr. Sanders intends, in renouncing fat-cat, super PAC campaigning that is turning American politics into an exercise in plutocracy.

Americans of ordinary means have made 400,000 donations — about 80 percent of them were $200 or less — to Mr. Sanders. Contrast that with the appalling fact that fewer than 400 of the nation’s most affluent families, writing six- and seven-figure checks, account for almost half the money raised so far by both parties in the campaign, according to an analysis by The Times.

The Sanders campaign, whatever its fate, has at least established that small-beer donors are alive and well and enthusiastic in America. What they and democracy need as a quid pro quo is a revival of the public financing system that protected politics after the corruption of the Watergate scandals.

As things stand now, the Supreme Court’s disastrous Citizens United decision has grossly boosted the buying power of corporate and special interest donors and made a casino frenzy of the race. The Koch brothers have proudly organized more than 400 of their wealthy allies to create a super war chest of $889 million for Republican candidates. The Jeb Bush campaign, pretending to remain at arm’s length from its supposedly independent super PACs, raised over $100 million so far in big-check donations. Hillary Rodham Clinton, aiming to stay competitive, has raised more than $20 million in super PAC money, much of it from millionaires, even as she pursues small-dollar donations and vows to do something about campaign reform.