Florida Gov. Rick Scott (R) on Tuesday tangled with Sen. Bill Nelson (D-Fla.) in a debate that will help shape one of the nation’s marquee Senate races this fall.

Hopes by Democrats of capturing control of the Senate probably depend upon holding the Florida seat Nelson has occupied since 2001. When the 2018 election cycle started, few analysts considered the three-term Nelson among the most vulnerable Democrats running for re-election. But Scott (pictured above left) jumped out to a small lead in early polls.

Nelson has since (pictured above right) battled back, tying or leading in the past four public polls. He also enjoys a fundraising advantage, having raised $19.7 million and a war chest of $14.6 million. That compares with $8.6 million raised by Scott, who had $3.3 million in the bank as of the most recent campaign finance report, according to the Center for Responsive Politics.

During their debate, televised by some Florida TV stations and the Spanish-language Telemundo 51, Scott sought to portray Nelson as a do-nothing senator with few accomplishments despite spending decades in Washington. Nelson, meanwhile, depicted Scott as a dishonest politician who failed as governor.

Here the five biggest themes of the debate.

1.) Whether Nelson has had any impact as senator. This was Scott’s go-to talking point. Every time Nelson raised an issue, Scott reminded viewers that the incumbent senator has spent more than four decades in Washington, including his previous tenure in the House of Representatives.

“He’s been there when his party controlled both houses and the White House. He’s done nothing,” Scott said after Nelson complained about the country’s broken immigration system.

At another point, Scott said, “He can come here every six years and campaign. He can say things. But he’s been there for 42 years. Nothing’s happened.”

2.) Whether Scott is honest. If Scott leaned on attacks on Nelson’s lack of accomplishments, the Democrat returned again and again to his favorite theme: that the governor cannot be trusted.

“The governor keeps coming out with one whopper after another. Apparently, you never got your mouth washed out with soap for telling a lie,” Nelson said in one of his few zingers of the debate.

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At another point, Nelson said, “Whatever he says is simply not true.”

And the senator offered proof — analysis of Scott’s ads by professional fact-checking organizations.

“They’re all false or pants-on-fire false,” Nelson said. “The technique that my opponent tries to use is to distract.”

Scott responded by saying that Politifact, one of the best known of the fact-checkers, is basically an arm of the Democratic Party.

3.) Who is to blame for “red tides” and other algae blooms resulting from the release of polluted waters from Lake Okeechobee to the coasts. Nelson dismissed Scott’s stated efforts to solve the environmental crisis. Those claims are “disjointed from the truth,” the senator said.

“He has systematically disassembled the environmental agencies of this state,” he said. “He has drained the water management districts of funding. He even abolished the Department of Community Affairs.”

Scott fired back that he has increased funding for the Department of Environmental Management by 30 percent and also had earmarked $200 million for the Everglades.

The fault, Scott argued, rests with Nelson.

“Sen. Nelson has gotten us no money to fix the dyke on Lake Okeechobee,” he said.

4.) Whether Florida’s voting system is secure. Nelson made news earlier this year when he declared — without offering evidence — that Russians had gained access to Florida’s voting system and had “free rein to move about.”

Nelson on Tuesday parried attacks by Scott, calling it a “cheap political trick” that should not fool voters. “We have to be constantly concerned about the security of our election. The governor continues to bring up issues to try to distract from his record.”

Scott questioned why Nelson would not explain himself.

“The senator did not respond about things that he said … Either he made it up or he tried to make people feel uncomfortable,” he said.

5.) Where the candidates agreed that they disagree. Often, debates are exercises in obfuscation, with both candidates obscuring differences on issues to appeal to the middle of the electorate. This especially is true in swing states like Florida.

But at times Tuesday, the debate proved clarifying. Nelson proudly embraced Obamacare and criticized Scott for not expanding Medicaid to cover more of the working poor.

“For the seven years of the law, my opponent has wanted to kill it, repeal it,” Nelson said.

Scott did not dispute it. He noted that premiums have gone up and choice has gone down since the Affordable Care Act passed. What’s more, some people found they could not keep their doctor or their health plans under the law, he said.

“If there was a lemon law, that should be sent back immediately,” he said.

Scott and Nelson also agreed that they disagree on gun control. Nelson called for banning so-called assault rifles.

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“My opponent has an A-plus rating with the NRA,” he said. “He has passed more NRA-backed legislation than any other governor in the history of this state.”

Scott said he supports the Second Amendment but also wants to make schools safer and noted that he had signed legislation to put more law enforcement officers and mental health counselors in schools.

“Here’s the difference. Sen. Nelson said he is fine with taking away certain guns from law-abiding citizens,” he said. “I think we ought to focus on the problem. The problem is we have people who want to harm themselves or others. And I think we ought to take away all weapons from them.”