Alice Walton of Bentonville, Ark., is a big supporter of Hillary Clinton becoming the Democratic presidential nominee in 2016.

Walton gave $25,000, the maximum allowed under federal law, to the super PAC Ready for Hillary during the 2013-2014 cycle, according to filings with the Federal Election Commission. Walton is a long-time acquaintance of Clinton, going back to the former secretary of state's days as Arkansas' first lady.

Walton is also the daughter of Sam Walton, founder of the Walmart chain of big-box retail stores. That makes the donation a rather delicate matter for Clinton, the front-runner for her party's nomination. For many on the Left, the Arkansas company is emblematic of all that is wrong with corporate America. It is particularly detested by organized labor — a key Democratic constituency — because the company has doggedly fought all efforts to organize its workers.

Clinton's ties to Walmart go back to 1986, when she joined the company's board of directors. She remained there until 1992, when husband Bill Clinton ran for the White House. For years afterwards they both maintained close ties to the retail giant. More recently, Clinton has distanced herself from the company and criticized some of its business practices.

It is a delicate matter that the company and the candidate are both loathe to discuss. A spokesman for Walmart had no comment. A spokesman for the Walton family did not respond to a request for comment. Nor did Ready for Hillary. Don Soderquist, the board's vice chairman during Clinton's tenure, declined to comment. Clinton makes only a single, passing reference to her years in the board in her 2003 memoir, Living History.

Those ties, nevertheless, remain a cause for suspicion of Clinton among liberal activists, many of whom are concerned that her candidacy will keep the Democratic Party from going further in the economically populist, anti-Wall Street direction they think it should.

"It was 20 years ago but it does speak to a closeness Hillary Clinton has to corporate interests on Wall Street and beyond," said a veteran progressive strategist who asked to remain anonymous. "The base of the party is increasingly concerned about our political leaders being too tied, too close, and owing too much to corporate interests, whether those corporate interests are located on Wall Street or in Arkansas."

Numerous liberal organizations have called for a more economically progressive candidate to jump into the race. "The desire for an alternative to Clinton is real [and] ... We share that desire," the Nation wrote in a November editorial. The groups and Democracy for America have pledged to spend more than $1 million on campaign to draft Sen. Elizabeth Warren, D-Mass., running ads in the key early primary state of New Hampshire.

Clinton is still widely favored to win the Democratic nomination, but the Walmart connection continues to haunt her. References to it often turn up in the liberal press. "Clinton's public comments may have turned against the Arkansas company, but the ties haven't been completely severed," Mother Jones reported last year. Liberal criticism of Walmart has grown stronger in recent years as organized labor has stepped up its campaign against the non-union company.

In a 2004 speech, the former secretary of state said Sam Walton himself called her one day and asked her to serve on the board. Walmart was being criticized at the time for its lack of women in upper management — Clinton became the first woman to serve on the board of the company. Bill Clinton was Arkansas governor at the time and the Clintons and the Waltons knew each other socially. According to a 2007 Los Angeles Times story, Alice Walton pushed her father to take Hillary Clinton on as a board member.

Clinton also worked at the Rose Law Firm, which represented Walmart. A 1994 New York Times story identified Clinton as the firm's lead lawyer for the company.

As a board member, Clinton was paid $18,000 annually plus $1,500 for each meeting she attended, according to a 2006 Associated Press story. By 1993, the Clintons had $100,000 in Walmart stock, which was put into a blind trust after the 1992 election. They flew on the Walmart corporate jet 14 times during 1990 and 1991.

By all accounts, Clinton pushed the company to hire more women and to address environmental issues. She was silent on other issues, though, never questioning the company's anti-union stance, for example. That plagued her through the 2008 election after ABC news unearthed some video recordings of company events that included her. "I'm always proud of Walmart and what we do and the way we do it better than anybody else," she said at a 1990 stockholders meeting.

"She was not a dissenter," Soderquist told the Los Angeles Times in 2007.

Then-presidential candidate Barack Obama used the issue in a January 2008 presidential debate, telling Clinton: "[W]hile I was working on those streets watching those folks see their jobs shift overseas, you were a corporate lawyer sitting on the board at Walmart."

Later that month, Bill Clinton defended her tenure, telling ABC that they "lived in a state that had a very weak labor movement ... she knew there was no way to change that, not with it headquartered in Arkansas."

Clinton eventually returned a $5,000 donation from Walmart's political action committee that year, saying that the company's "policies do not reflect the best way of doing business and the values that I think are important in America." Her campaign did not return another in $20,000 in contributions from Walmart executives and lobbyists, though.

The ties between the Clintons and the Walton family continue to this day. The Walmart Foundation and the Walton Family Foundation each have given between $1 million and $5 million to the Clinton Foundation, according to the latter's website.