Senator Sanders is emailing supporters to highlight the fact that his opponent in the Democratic presidential primary, Hillary Clinton, is being supported by “enormous checks from people like Alice Walton (yes, Wal-Mart).” And it is true. Federal campaign finance records show that Ms. Walton, of Bentonville, Arkansas, gave Hillary Clinton’s campaign $2,700, and then wrote another check, for $353,400, to the “Hillary Victory Fund.”

The support for Mrs. Clinton’s campaign represents something of a political shift for Ms. Walton. Previously, her large donations had mainly gone to Republicans. The Federal Election Commission records show she donated a total of $200,000 in 2011 and 2012 to a committee backing Mitt Romney, a Republican presidential candidate, and a total of $2 million in 2004 to a group supporting President George W. Bush’s reelection. Additional contributions of more than $150,000 in the past dozen years have gone to groups supporting Republican candidates for the House and Senate.

Senator Sanders seems to think that voters who view Wal-Mart as the embodiment of evil will be horrified to learn of Ms. Walton’s support for Mrs. Clinton. Maybe some voters will indeed recoil at the news. But as an optimist and as a supporter of free markets, I view it as a hopeful sign that Mrs. Clinton is returning to her senses about Wal-Mart.

“Returning” is the key word, because there is a substantial history here. As The New York Sun reported in a 2006 editorial, when Mrs. Clinton’s husband was an Arkansas politician and she was the real breadwinner in the family, she served, between 1986 and 1992, as a member of Wal-Mart’s corporate board of directors. By 2006, when Mrs. Clinton was serving as a United States senator from New York, she returned a $5,000 contribution from the Wal-Mart political action committee, explaining via an aide that she had “serious differences” with the company’s practices.

Now, a decade later, with Mrs. Clinton running for president, Wal-Mart’s money — or at least Alice Walton’s — is acceptable anew to Mrs. Clinton and to her ostensibly independent victory fund. Whatever the reason for Mrs. Clinton’s reversal — or for Ms. Walton’s — it would certainly be good for the country if presidential candidate Clinton were to learn some things from Wal-Mart. The company and the Walton family have ideas on topics like wages, health care, education, banking, the Second Amendment, and even the environment.

On health care, the $4 generic drugs available at Wal-Mart’s pharmacy are a fine example of how free-market, private-sector capitalist competition, rather than top-down government-imposed price controls, can make medicine affordable for patients.

On education, the Walton Family Foundation says it has supported a quarter of the 6,700 charter schools in the U.S. and it is investing in what it describes as “the high-quality choice movement.” That’s a counterweight to the Clinton campaign’s backers in the teacher unions. Those unions too often see charter schools as threats that siphons money away from schools that employ unionized teachers.

On the Second Amendment, anti-gun activists have publicly called on Wal-Mart to stop selling guns and ammunition in its stores. The store has voluntarily stopped selling some models of rifles, but it continues to sell handguns and other weapons, evidence that businesses are best left to their own judgments on these matters to respond to customer sentiments and demand without congressional interference.

On banking, the extensive financial services that Wal-Mart offers its customers — not only check cashing, but also bill-paying, tax preparation, and a “bluebird” financial account that claims to offer the “benefits of banking without all the fees” — demonstrates how non-bank firms are filling a market gap. Rather than forcing banks with regulations to provide these services or subsidizing the banks with bailouts, why not let the free market work?

On wages, Wal-Mart has been raising pay even without a congressionally mandated increase in the federal minimum wage. And on environmental issues, Wal-Mart has been taking a range of steps — using closed freezers instead of open ones, and putting skylights in stores, using sunshine to save on lighting bills — because they make financial sense, not because they were forced to do so by government rules.

So yes, Senator Sanders is trying to scare his supporters with emails linking Mrs. Clinton to Wal-Mart. To the non-socialists among us, such a connection is not so much scary as it is at least somewhat reassuring.

Mr. Stoll is editor of FutureOfCapitalism.com.