INDIAN RIVER, Fla. — The beaches along this affluent east coast stretch of Florida on a recent Friday were occupied only by the rotting fish that had washed ashore from the deadly red tide and the vultures that circled above.

Residents insisted the smell wasn’t as bad as it had been lately because the wind that day was blowing from the west, keeping the stench offshore.

While the area may have gotten a temporary break from the weather, businesses and workers here have not. At the iconic Ocean Grill on the water in Vero Beach, business was worse this month than any in recent memory residents say. The odor on a recent day was so putrid that even with the windows to the restaurant closed, the workers and the few patrons coughed and felt a burning sensation in their chest, one bartender recalled.

Florida's growing environmental problems have become a top concern to voters here, forcing candidates from both parties up and down the coasts to address the issue as it threatens to upend an election that was once expected to be a referendum on President Donald Trump.

And it is long overdue, according to observers here. "It’s a complex problem and it’s been building for years," said Susan MacManus, a long-time political scientist at the University of South Florida. "For three or four years it’s been showing up in polls and the environment has seeped into the top five issues.”

The red tide that stretches from Cape Canaveral to West Palm Beach has joined a similar long-running disaster on the west coast of the state in influencing the political discussion here.

In an election year dominated by national events, Florida is showing that local issues like this could yet prove decisive. It's become a top issue in at least six hotly contested congressional races currently held by Republicans, as well as in the state's tight senate and gubernatorial races.

And it's not breaking down along predictable party lines. Even Republicans, who have shunned environmental issues as campaign priorities in recent years, are defending their environmental record and have vowed to clean up Florida.

Throughout a state where the environment is a major economic concern — driving tourism, commercial fishing and real estate — voters are demanding that candidates prioritize cleaning up their toxic water. Fifty percent of respondents in a recent poll saying that the state isn't doing enough to address climate change.

"The power of the visuals day-in and day-out of the algae bloom and the dead fish, and its impact on commercial fishing in Republican areas has elevated it to the top of the priority list for voters," said MacManus.

When asked about her view of this fall's elections, Vero Beach realtor Holly Benke, a GOP-leaning voter, told NBC News unprompted that the environment is her biggest concern.

"My priority is definitely the environment and I want to see healthy water ecosystems here and in Lake Okeechobee," Benke said, referring to a large natural lake that is a critical factor in Florida's ecosystem. "I'm not really keen on what's going on locally. I think (gubernatorial candidate Andrew) Gillum looks great."

A sign that reads, "Beaches closed due to red tide," in Vero Beach, Florida. Leigh Ann Caldwell / NBC News

Florida is facing a series of environmental challenges, including rising ocean levels, increasingly strong and frequent hurricanes, blue-green algae blooms that have closed beaches on the west coast of the state, and now, the red tide, which has kept 100 miles of beaches closed on the east coast for most of October.

Gov. Scott, who entered office eight years ago, at the start of a recession that hammered the state’s economy, vowed to prioritize jobs and economic recovery. He slashed funding of environmental agencies, including $700 million for water management — or 40 percent of its budget — in his first year in office, but in later years he added $300 million back in. He gutted environmental protection regulations and state officials have said that he prohibited agencies from using the term climate change.

Now the GOP Senate nominee, Scott is attempting to soften his environmental credentials, vowing to protect Florida’s waters, and blaming incumbent Democratic Sen. Bill Nelson and the federal government for inaction.

"This is a conspiracy theory peddled by the Democrats that is completely false," Scott spokesman Chris Hartline, said in a statement. "There is not, nor has there ever been, any policy forbidding the words 'climate change," 'global warming,' or any other term. Governor Scott has invested hundreds of millions of dollars to address sea level rise, including over $300 million for flood mitigation, coastal resiliency, beach renourishment and coral reef protection."

Democrats say Scott’s environmental rehab isn’t working. They point to primary election results where Rick Scott received just 80 percent of the Republican vote against an unfunded candidate in Martin County, ground zero of the blue-green algae problem. Democrats insist it's a protest vote against Scott’s environmental policies.

"It’s a bit of irony that Rick Scott has spent so much of his career trying to gut environmental protections and there’s a massive environmental catastrophe that is costing him support," said David Bergstein, press secretary of the Senate Democrat’s campaign arm, the DSCC.

The issue is also taking center stage in the gubernatorial race, where the Republican candidate, Rep. Ron DeSantis, being weighed down by Scott’s record.

At a rally last week in support of Tallahassee Mayor Andrew Gillum, the Democratic nominee, former Vice President Joe Biden pointedly noted that Florida officials will once again be able to say "climate change" with a Gillum administration.

As a nod to the importance of the issue, DeSantis, an avid supporter of President Donald Trump who has questioned human contribution to climate change, highlighted Florida’s toxic waters in his 60-second opening remarks at a debate last week.

"I ran in the Republican primary stressing the need for clean water. I stood up to the most entrenched interests in Florida. I had $17 million spent against me, many of that from people who opposed my view on cleaning up our water," he said.

But DeSantis, who was endorsed by the GOP-leaning Everglades Trust, cautioned that he wouldn’t go too far. "What I don't want to do is do things like what Andrew wants to do which is do a California-style energy policy that will cause our electricity rates to skyrocket 20 percent, 30 percent," he said. "That's going to hurt senior citizens on a fixed income. That will hurt our blue collar workers."

Gillum, who has been endorsed by most of the environmental groups in Florida, says he would be a better steward of Florida’s air and water.

"For 20 years, we've handed over the keys of environmental protection in this state to, quite frankly, again, the biggest corporate polluters," Gillum said. "I’m going to have the courage of my conviction to hold those folks who are the biggest polluters accountable and responsible for the degradation of our environment."

With all of the beaches in Republican Rep. Brian Mast’s district closed due to the red tide, he’s made climate change central to his re-election effort and the embattled congressman has said he won't endorse Gov. Scott because of the issue.

Mast, a member of the climate change caucus in the House of Representatives along with several other Florida Republicans, released an attack ad against his Democratic opponent, Lauren Baer, on the toxic water.

"When asked what was the most important issue in the district, Lauren Baer said that it was not the toxic water. That's right, not the toxic water," the narrator in the ad said.

Baer’s campaign responded with their own TV ad. "Since Brian Mast has been in congress, he's taken over eighty thousand dollars from polluters and consistently voted to eliminate protections for our water. The algae crisis has gotten worse. Our water and economy can't take another two years of Brian Mast," the narrator said.

In the race to fill DeSantis' congressional seat, which is also impacted by the red tide, Republican Mike Waltz and Democrat Nancy Soderberg are battling over the issue. And in south Florida, Rep. Carlos Curbelo and his opponent Debbie Mucarsel-Powell both say rising ocean waters is a central concern to voters.

A similar theme in attack ads from both sides is campaign contributions from the industry. And that’s because it resonates with voters who say that politicians won’t stand up to the biggest polluters of Florida’s waters: the sugar industry, agriculture and developers.

While politicians fight and try to win election to implement plans that could take years to clean up Florida’s waters, residents are being financially and physically impacted now.

Visit Florida, the name of the state’s tourism industry, is launching $9 million worth of ads across the country to entice tourists to come to the beaches that are open.