As election season heats up in Florida paradise, there is more than one red vs. blue battle being waged on the state's southeastern shores — and it's one of the most critical political issues ahead of November.

Red tide, a toxic algae bloom that occurs naturally in Florida's blue saltwater, has been particularly invasive and intense on the state's southeastern coastline recent months, forcing Florida to call a state of emergency last week. It's become the subject of campaign ads, as Democratic Sen. Bill Nelson and term-limited Republican Gov. Rick Scott blame each other for the problem as they run for Nelson's Senate seat. And in Florida's governor race, one of the most contentious gubernatorial races in this country this fall, even the Trump-aligned GOP gubernatorial hopeful Ron DeSantis has made algae of a different color a key issue, as blue-green algae caused by pollutants plagues the state's freshwater bodies.

The environment is already a major issue in Florida — it's what attracts so many to live there, said Susan MacManus, a longtime Florida political analyst who recently retired from teaching political science at the University of South Florida. But lately, environmental concerns have become so prevalent that even candidates in the generally conservative eastern part of the state are talking about it.

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"Every candidate has been mentioning the environment," she said. "...The issue now has reached across both sides of the aisle."

Red tide has been a phenomenon for centuries, said Stephen Leatherman, an earth and environment professor at Florida International University.

"Why didn't you hear about it before? Well, this is a big one," he said. Although it's not known to be directly linked to runoff pollution, once it moves in closer to the coastal areas, the red algae, Karenia brevis, may also feed on nutrients from polluted runoff.

The red algae is killing off sea life and commercial fishing, dampening the tourism industry, and worrying seaside residents about air quality, since the toxins, Leatherman said, can also be airborne.

"It's a priority," Leatherman said of how much the toxic algae issue is affecting the political environment this fall. "The problem is, it's such a big issue — how do you get your hands on it?"

Nelson and Scott, who are neck and neck in the polls as November approaches, have both blamed each other for failing to do enough about the problem.

"Washington politician Bill Nelson made a pledge 30 years ago to solve this problem," Scott said in an ad earlier this month. "But Nelson's a talker, not a doer. With Bill Nelson, we get more waiting, more talk, and more algae."

Then Rick Scott appears on screen. "I'm Rick Scott. I don't wait for Washington. And I approve this message."

Nelson fired back with his own ad, which shows slides with newspaper clippings and says, "Rick Scott cut environmental protections. Rick Scott gave polluters a pass."

Nelson and Republican Sen. Marco Rubio introduced a bill on Thursday that would require a federal algae department to make a plan to mitigate and control harmful blooms in southern Florida.

"These toxic algae blooms are choking Florida's waterways, crippling our economy and making people sick," Nelson said in a statement. "We need all hands on deck to help, and this bill will provide scientists and researchers the resources they need to understand what's causing these harmful algae blooms – and what needs to be done to stop them."

Although scientists are trying to figure out how to control red algae, there is still no clear solution to completely remove the algae without harming the ecosystem, according to Mote Marine Laboratory.

Meanwhile, in Florida's gubernatorial race, a different kind of algae has seeped into the campaign. In an unusual move for a conservative Republican, gubernatorial hopeful Rep. Ron DeSantis has railed against "Big Sugar" — a Florida industry some are blaming for pollution that contributes to a separate blue-green algae problem invading Florida fresh water bodies. Runoff from septic tanks and fertilizer is also a factor in the spread of blue-green algae. DeSantis is running for the GOP gubernatorial nomination against Adam Putnam, who is Florida's agriculture commissioner and the other top contender. Putnam's campaign and PAC have been fueled by millions from the sugar industry. DeSantis called Putnam an "errand boy" for U.S. sugar in a recent debate.

MacManus said she thinks the worst of the "finger pointing" might be over, as scientific explanations for the algae have entered into news coverage and politicians have to actually work together to solve the problem.

But it's a contentious political climate in Florida, with an open governor's race, competitive Senate seat, and a handful of House seats Democrats think they can flip to help take control of the House. Florida, MacManus said, has elevated itself on the national stage.

The polls in Florida's primaries close at 7 p.m.