Marijuana legalization proponents in Massachusetts can count Jonathan Bush, the CEO of Watertown-based health care company Athenahealth and a cousin of former President George W. Bush, in their corner.

According to state political finance records, Bush donated $10,000 to the Yes on 4 campaign, which seeks to legalize the use and sale of recreational marijuana in the state through a ballot initiative this November.

Bush was not available for an interview this week. But Athenahealth spokeswoman Holly Spring confirmed he had made a personal donation to the campaign.

“He believes this is one of many freedoms Americans should have the right to,’’ Spring said in an e-mail.

At the federal level, Bush has donated to the Libertarian presidential ticket, which supports marijuana legalization. He gave $2,700 to Gary Johnson’s campaign, which features former Massachusetts governor William F. Weld in the vice presidential slot.

Bush had previously donated to the campaign of his cousin, Jeb Bush, during his failed bid for the Republican presidential. That Bush has said he believes marijuana legalization should be a state issue.

Bush’s contribution to the legalization campaign is a relatively small blip in the nearly $2.5 million raised by Yes on 4 in 2016. The campaign’s principle backer is New Approach Political Action Committee, based in Washington, D.C., which has donated $2.1 million.

The opposition group, the Campaign for a Safe and Healthy Massachusetts, has raised about $363,000 in 2016, according to filings released last week. It came from a variety of sources, including Boston-based companies Markley Group and the Cronin Group.

Adam can be reached at adam.vaccaro@globe.com. Follow him on Twitter at @adamtvaccaro.