FORTUNE — Where same-sex marriage is concerned, it’s been an especially heated summer. Protests and counter-protests continue to simmer over Chick-fil-A president Dan T. Cathy’s comments that his fast food chain supports a “biblical definition of the family unit.”
At the same time, several high-profile executives are entering the debate, with marriage rights referenda set to appear on ballots this November in Washington, Minnesota, Maryland, and Maine. But the jury is still out on whether companies themselves will get involved — similar to the way some have in recent years — or if they’ll sit this one out, as many conservative groups are hoping.
Recently, Amazon (AMZN) CEO Jeff Bezos announced that he and his wife had given $2.5 million out of their own pockets to advance the same-sex marriage cause in Washington state. Preceding them were Microsoft’s (msft) founder Bill Gates and its current CEO Steve Ballmer. On June 29, they each donated $100,000 to the legalization campaign in the state. So did Microsoft itself, two months earlier, when it put $10,000 on the line. And at the end of May, a Starbucks (sbux) LGBT affinity group donated $1,740 to the cause.
In most cases, it’s rare for businesses to go public on a hot-button social issue, as it risks offending customers and shareholders. But in recent years, a growing number of corporations have taken stances on policies affecting gays and lesbians, more often with abstract endorsements than with actual donations.
Microsoft has a fairly long history of LGBT activism. In fact, the tech giant became the first member of the Fortune 500 to offer equal benefits to its LGBT employees back in 1993. It consistently leads in the Human Rights Campaign’s annual scorecard of corporate LGBT policies. And in 2009, the company gave $100,000 from its own coffers to the movement to pass Referendum 71, establishing domestic partnerships, according to public documents. Those records also show similar, but smaller, donations from Oregon-based Nike (nke). And back in 2008, Apple (aapl) reportedly poured $100,000 into the unsuccessful effort to block Proposition 8, which banned same-sex marriages in California (a federal appeals court overturned the ban in February).
It’s unique that these West Coast companies attached dollars, and not just their logos, to this cause. But they have kept fairly quiet about this bankrolling. Microsoft and Nike declined to offer specific comment for this story. Instead, both companies offered prepared statements on workplace diversity and pledges to back LGBT rights. As for Starbucks, spokesperson Zack Hutson says the company supports the upcoming Referendum 74 to approve same-sex marriage, but won’t be donating.
Even Marc Solomon, the national campaign director for Freedom to Marry, says he didn’t realize the extent of high-level corporate spending on the issue. “I knew [Microsoft] endorsed, but not that they gave under the corporate name.… They should do it again!” Solomon says.
Zach Silk, campaign manager for Washington United for Marriage, is confident that his organization’s pro-LGBT business coalition will keep growing — and perhaps donating — into the fall. “This issue is at a tipping point,” Silk says. The campaign has raised $5.3 million to support its effort this election season, with donations coming primarily from individuals, Silk says. Coalition members — which seems to involve little more than attaching a company logo to the cause — include companies like Microsoft, Nike, Starbucks, Google (goog), Amazon, and Alcoa (AA), according to the campaign’s website.
Over in Minnesota, a proposed constitutional amendment would ban same-sex marriage. Just two of the state’s Fortune 500 companies have openly stated their opposition to the ban: St. Jude Medical (stj) and General Mills (gis), both of which declined to offer comment for this story. Although Target (tgt) released a gay pride-themed shirt earlier this year, a spokesperson for the Minneapolis-based retailer told Fortune in an email that it encourages employees to vote, but limits its position there. Kate Brickman, press secretary for Minnesotans United for All Families, the official campaign against the ban, confirmed that none of the $5.7 million the organization has raised so far has come from corporations.
Even before the Supreme Court’s 2010 Citizens United ruling, which has given corporations a much freer hand to use their money for political purposes, companies have been able to spend unlimited amounts on state ballot initiatives. In fact, Bruce Freed, director of the Center for Political Accountability, pointed out that corporations can avoid public disclosure requirements by spending indirectly, through a trade association or certain non-profits. Otherwise, a corporation would have to explain to shareholders that a political contribution directly serves its business interests. With same-sex marriage, the standard corporate argument in favor of the cause is that it amounts to a talent recruitment issue.
Opponents of same-sex marriage have urged corporations to stay neutral on the issue. Tom Minnery, a senior vice president of Focus on the Family, says that assuming either position will damage a company’s reputation, but not necessarily its sales. “Any criticism of a brand name is a concern, whether it drives sales down or not.” Boycotts against Starbucks, General Mills, and Chick-fil-A haven’t appeared to significantly affect the companies’ bottom lines. If anything, companies taking a side have benefited from the publicity, with Chick-fil-A claiming record sales last week.
Even so, Monica Cole, head of conservative-leaning One Million Moms, thinks corporations would do better investing in themselves than getting involved in controversial politics. “We’re not asking them to promote traditional marriage,” says Cole, whose evangelical organization has called for boycotts of Home Depot (hd) and JC Penney (jcp), based on claims that the companies support the LGBT agenda. “These companies should really focus on customer service and the quality of their products.”
Across the political divide, at Freedom to Marry, Eric Solomon thinks it’s noteworthy that conservative advocates are calling for corporations to sit out this debate, arguing that they “wouldn’t be asking for neutrality if they believed corporations would take up their position. It’s because they’re losing.”