An organization largely unknown in Florida politics is airing what appears to be the first negative ad against Republican gubernatorial candidate Adam Putnam.

The ad from a group called the Tenth Amendment Project focuses on the Lake Okeechobee crisis of 2016, when toxic algae blooms threatened the health of the state's largest freshwater body and surrounding ecosystems.

It lays that environmental disaster at the feet of the sugar industry, one of Putnam's largest campaign donors. The ad claims that Putnam as the state's agriculture commissioner, "let them pollute the Everglades and ruin our beaches and drinking water."

"Adam Putnam wants to be governor and Big Sugar is supporting him again so they can keep profiting at the expense of our clean drinking water," a narrator says.

U.S. Sugar has directly contributed $560,000 to Putnam's campaign and indirectly contributed even more through various organizations, like Associated Industries of Florida. Putnam is running against Rep. Ron DeSantis, who as a Congressman has voted against subsidies for sugar farmers.

Putnam spokeswoman Meredith Beatrice called the ad "categorically false." She said Putnam has secured "more than $1 billion in federal funding for Everglades restoration" and "worked with Governor (Rick) Scott to push the federal government to expedite repairs to the Herbert Hoover Dike surrounding Lake Okeechobee."

"Congressman DeSantis and whatever dark group he's got pushing this message would know this if he spent more than one day a month in the state he wants to lead," Beatrice said.

In the past, Putnam has said criticism of the sugar industry is often unfair and unhelpful in finding solutions to cleanup the Everglades.

"I think they're a viable, vibrant part of our economy, and the water that leaves sugar farms is cleaner than the water that comes on to them," Putnam said last year at the Forum Club of Palm Beaches. "And somebody's got to let science back into this conversation. You can be for cleaning up Lake Okeechobee. You can be for saving the Everglades. You can be for a strong economy. But all of us have to get out of the habit of thinking that there's just some simple answer of just you know take out the bad guys. And everything else is going to be fine."

It's not clear who is behind the Tenth Amendment Project. The group has only been involved in a handful of states, including South Dakota and Oklahoma. According to a Federal Communication Commission advertising form, the group shares a Washington, D.C., office with Sentinel Strategic, a firm with a roster mostly of Republican consultants.

Sentinel Strategic has not responded to a request for comment.