Voters weigh candidates' stance on many issues when entering the voting booth. The economy, taxes, public education and crime typically top the list.

But with toxic algae smothering large swaths of Florida's east and west coastlines, the environment may be the hottest issue in this year's U.S. Senate race, News 6 partner Florida Today reported.

"I'm a single-issue voter for the environment this year," said Cristina Maldonado, a veterinarian from Stuart. "Our state is on the verge of collapse environmentally. Every single waterway in the state is affected. So this year, yeah, the environment is my only issue."

In the face of that kind of voter passion, the Democratic incumbent Sen. Bill Nelson and his GOP challenger, Florida Gov. Rick Scott, have blamed each other for the state's environmental crisis.

Scott has run a TV ad accusing Nelson of having done nothing during his time in Congress to improve the situation with Lake Okeechobee. Seasonal discharges from the lake have fueled toxic algae blooms along the Treasure Coast and in Southwest Florida.

Nelson responded with his own ad that ended with "the water is murky, but the fact is clear: Rick Scott caused this problem."

While water quality is a problem throughout the state, the images of green, slimy waters and dead marine life along both the Atlantic and Gulf coasts of South Florida has made Lake Okeechobee discharges the center of the environmental debate.

Whenever heavy rains raise Lake O's water level, the Army Corps of Engineers, which controls the dike surrounding the lake, releases billions of gallons of water from the lake through canals that lead to the Treasure Coast to the east and the Fort Myers/Naples area to the west.

Since the federal government controls those discharges, Scott blames Nelson for not doing more to stop it.

Full Screen 1 / 83 A fishkill at the Coral Shores neighborhood in Bradenton. Photo taken on Aug. 14, 2018 by Dylan Jon Wade Cox.

But not lowering the lake's water level would threaten the integrity of the Herbert Hoover Dike. If the dike were breached, towns along the lake would be flooded.

And while the Army Corps controls the releases of water from Lake O, it doesn't control the quality of the water in the lake. The lake is typically plagued with algae fed by nutrients flushed from the agricultural areas surrounding the lake.

Environmental groups across the state have been harshly critical of Scott's tenure in Tallahassee, saying his administration's budgets cuts for environmental programs helped lead to the water problems now plaguing the state.

Among their criticisms:

Slashing the budgets of the state's seven water management districts, which oversee water issues throughout the state. The state's 2012 budget — the first under Scott's administration — cut $700 million from the agencies. Since then, their total budgets have gone up by about $300 million, but remain far below the levels they were when Scott took office.

A sharp decrease in the enforcement of environmental regulations. According to Florida Public Employees for Environmental Responsibility, the state's Department of Environmental Protection opened some 1,600 investigations into potential environmental violations in 2010, the year Scott was elected to office. By 2017, that number had dropped to 220 new cases.

Ignoring the will of voters who in 2014 approved by a 75 percent vote setting aside one-third of real estate transaction taxes for conservation efforts. A coalition of environmental groups sued the state, saying the money was being used to pay for things normally covered by general funds revenue rather than new conservation efforts. A circuit court judge in June ruled in favor of the environmentalists. The state has appealed the ruling.

Environmentalists also point to the Legislature for its role in cutting back on conservation efforts. But they lay the lion's share of the blame on Scott as the state's top elected official.

Kevin Curtis, executive director of the National Resources Defense Council, is particularly blunt in his assessment of Scott's oversight of the environment during his two years of government.

“Governor Scott has regularly put the wishes of corporate polluters above the needs of Florida’s environment and families," Curtis wrote in a position paper posted to the group's website. "He’s sided with a fringe movement of climate change deniers, defunded popular and bipartisan conservation programs, and undermined the enforcement of air, water and climate protections. If you value Florida’s natural resources, a strong economy and a safe future for our children, casting a vote to put Rick Scott in the Senate makes zero sense. Senator Nelson is the clear, best choice in this race.”

Not every voter agrees.

Kirk Newkirk owns Key Sailing, a Pensacola Beach business that rents watersports equipment and provides boat tours. He said Scott has been a “fantastic” governor who made great business decisions that benefited all of Florida.

The map below, provided by the Florida Department of Environmental Protection, details algal bloom sampling results across the state.

By contrast, “Bill Nelson is more of a South Florida-type of person, a special interest type of person,” Newkirk said, noting Nelson had received hefty sums of money from the sugar industry.

Addressing the state’s current environmental health — particularly the algae blooms in South Florida — Newkirk noted there was enough blame to go around, but added some politicians carry more blame than others.

“Both have dragged their feet, but Bill Nelson has been in office for 20-something years,” Newkirk said. “Rick Scott has only been governor for eight.”

Newkirk raises an issue that Nelson must deal with when it comes to the environment. While Nelson can point to many things Scott did wrong regarding environmental issues, he can't point to many successes he has had himself.

States are generally responsible for setting and policing the environmental quality standards for their citizens and businesses. But Congress plays an important role as well, creating policy for the use of federal lands within states and funding federal programs such as national park upkeep and cleanup of Superfund toxic waste sites.

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Members of Congress also play a role in helping to steer money to environmental programs coordinated by the Army Corps, such as Everglades restoration, though the executive branch largely decides which specific projects received funding.

[Blue-green algae: An explainer on the sludge blanketing Lake Okeechobee]

While Nelson has introduced several bills in recent years to help deal with the Lake O crisis, he hasn't managed to get one of them through the Republican-controlled Congress.

Nelson refused to support a congressional bill that would have done away with subsidies and other federal policies to prop up domestic sugar prices. Those policies make the land controlled by Big Sugar south of Lake O — land critical to plans to handle Lake O overflows and Everglades restoration — more valuable, meaning sugar producers are less likely to sell the land needed for environmental projects.

Amy Hickel, a Cape Coral small-business owner, said via email that Nelson "hasn't accomplished anything where our water issues are concerned," during his time as senator. She said Rick Scott hasn't done much as governor either, but she'd probably vote for him at this time and hope for a chance at representation, because he "doesn't have a track record in D.C. of doing nothing."

Scott's critics, though, point out the governor of any state has much more control over the environment than any single senator, who is just one voice in a body of 100.

"He hasn't done anything positive," Naples fisherman Capt. Bill D'Antuono said of Scott. "It’s almost like he has made a deliberate attack on the environment and my way of life by dismantling protections. I would never vote for him in a million years."

[READ: Florida's toxic algae: Red tide. Green slime. Be careful.]

D'Antuono says "100 percent of his vote" will be about the environment. But while he said he wouldn't vote for Scott, he is not all that thrilled about Nelson, either.

"Nelson has a record of taking money from sugar but has also proposed tax breaks to business affected by red tide and Lake Okeechobee. Unfortunately, it’s like a lesser of two evils."

Ron Austin, commodore of the Southwest Florida Yacht Club in Fort Myers, said the crisis has changed a lot of the club's plans for the year, and the boaters are disappointed.

He said he'd want to see the next senator work with Congress to fund the restoration of the movement of water south, "where it historically has gone," put filtration systems in place, build the necessary reservoirs and dams, and to get started as soon as possible. But he has little hope that either Nelson or Scott would "have the support to change anything," adding that it would be business as usual.

"There's got to be a way to put this together so that we don't take farmers and Big Sugar out of business, and we have clean water," he said.