The Florida Senate race has given Democrats plenty of reason to be nervous this year.

Democratic Sen. Bill Nelson is facing Republican Gov. Rick Scott, one of the best recruits for Republicans in the 2018 midterm elections and a wealthy candidate whose campaign is already outspending Nelson’s by a 4-to-1 margin. The two faced off in a debate on Tuesday night.

Nelson has built a reasonably strong brand, representing Florida in the Senate since 2001. Scott, meanwhile, has never won a race by more than a point in years friendlier to the GOP. But the GOP governor is still a serious threat in a state where elections are rarely decided by more than a point or two.

For most of the summer, Scott had jumped out to a slim lead in the polling — and a major advantage in campaign spending, spending more than $27 million to Nelson’s $6 million, according to Open Secrets. Democrats have had to hope the lopsided spending explained the Republican lead in the polls and can therefore be corrected as their own spending picks up in the last weeks of the campaign.

“Having been in the fight with Scott in the past, there is a flow to the way they campaign: they use their financial advantage to get on TV early, and Scott, to his credit, is tireless on the stump,” Steve Schale, a Democratic operative in Florida, told me. “So am I worried about Nelson? Sure, but not any more or less than any Democrat running in a competitive race here. This race was always destined to be close, it is just how Florida works these days, for better or worse.”

Florida is one of 2018’s marquee — and probably its most expensive — Senate races. Democrats are on defense in yet another state Trump won in 2016. They can’t afford to lose any additional seats if they’re to have any hope of reclaiming the majority.

“The two biggest determinants in the Senate race are, one, resources and, two, Donald Trump,” Mac Stipanovich, a longtime Republican operative in Florida, told me earlier this year. “Either one of them can win, but my sense is that if Nelson has comparable resources then the governor is the underdog.”

Why Rick Scott’s Florida Senate candidacy is such a big deal

Scott’s candidacy was long expected. Trump and Washington Republicans had been courting him. He is term-limited at the end of this year, after his two four-year terms as governor. He doesn’t really have anything else to do.

Rick Scott is also very, very rich, and he has shown before he’s willing to spend whatever it takes to win a statewide election in Florida.

He is worth about $150 million, according to the most recent estimates, after making his money as a hospital executive. He spent $75 million of his own money to win the 2010 gubernatorial race — his first political campaign of any kind — and another $13 million in his 2014 reelection campaign.

Scott never won big: He beat Alex Sink by 1.2 percentage points in 2010 and Charlie Crist by 1 point in 2014. But he did win.

“With Scott, this is a guy who’s been told he can’t do something like this twice, and twice proven everybody wrong,” Schale told me. “A more conventional politician might look at national mood and think, ‘Wow, this could be really uphill.’ Scott’s view is: ‘You told me I couldn’t win the first time, and I won. Why would I listen to you now?’”

Scott’s candidacy is also important from a national perspective. Republicans theoretically have a lot of Senate pickup opportunities this year; Nelson is one of 10 Democrats up for reelection in a state that Trump won in 2016. But they have at times struggled to attract top-tier candidates. To give one example: Democratic Sen. Jon Tester, representing Montana, a state that Trump won by 21 points, is still rated lean Democratic by the Cook Political Report because his GOP opponent isn’t considered top-notch and Tester has polled well.

The Florida governor, on the other hand, is a hardened, well-qualified, and sure to be well-funded candidate. Scott has forced Democrats to take Florida seriously and to invest the necessary time and money into the race to make sure Nelson beats Scott. This race has demanded resources Democrats otherwise could have spent defending their other more vulnerable incumbents or going on offense in states like Arizona, Nevada, or Mississippi.

Republicans currently hold a slim 51-49 advantage in the Senate. Democrats are defending seven of the 10 most competitive races this fall, and need to hold on to every seat they can — including, now, Florida, which Cook rates as a toss-up — if they want a shot at a majority.

“This is a very competitive race, and if the Democrats don’t lay out on it, they’ll lose. They are going to have to step up and help Bill Nelson,” Stipanovich said. “If Scott outspends him 2 to 1, it’s quite likely that Gov. Scott will prevail.”

The current spending figures give Scott that kind of advantage: Open Secret reports that Scott has raised $31 million to Nelson’s $20 million and spent nearly $28 million to Nelson’s $6 million.

Perhaps as a result, Real Clear Politics had Scott leading Nelson by one or two points on average in the polls, until recently. Nelson now holds an equally slim 1.1-point advantage, after a couple of strong surveys. It’s a very close race.

The charisma-free Rick Scott versus Bill Nelson campaign, previewed

As for the candidates themselves, the Florida Senate race has been lacking in charisma. That was clear again in Tuesday night’s debate. Schale had previously said of his fellow Democrat Nelson: “Not a guy who’s lining up to give the keynote speech at the DNC. Not gonna break any records for his oratory skills.”

Regarding Scott, Stipanovich, the Republican operative, had said: “Gov. Scott doesn’t exactly light up the stage. He’s not the most dynamic and inspiring speaker.”

I profiled Scott in 2013 for Governing magazine and came away with much the same impression:

At the Florida statehouse for National Day of Prayer this May, for instance, the businessman who won Florida’s governorship in 2010 doesn’t work the room so much as he goes through the motions. He dons the same slight smile as each photo is taken. He exchanges a few friendly words with every person who approaches him in the large room on the 21st floor of the Capitol. Standing by the windows, he’s framed by an expansive view of Tallahassee and beyond, but he doesn’t own the scene. There isn’t the charisma you might associate with the governor of the fourth-largest state in the country.

Scott has tried to turn that to his advantage in his campaign.

“Let’s stop sending talkers to Washington. Let’s send some doers to Washington,” he said in his maiden campaign speech. It’s a theme he hits constantly throughout his campaign, portraying Nelson as an aging career politician with nothing to show for his many years in the Senate.

Nelson, meanwhile, has sought to paint Scott as a political opportunist who isn’t being honest about his record as Florida’s governor.

“While it’s clear that Rick Scott will say or do anything to get elected, I’ve always believed that if you just do the right thing, the politics will take care of itself,” he said in a statement.

They do have strengths, of course. Nelson has been elected in the state three times, after all, most recently by 13 points in 2012 — unheard of in a state where statewide elections are usually decided by a point or two. Schale praised the senator (who once famously went to space) for sticking to Florida-specific issues, like offshore drilling and Medicare for the state’s more elderly population, while mostly avoiding the high-profile spats in Washington on more contentious matters.

“Nelson does a pretty good job as well of avoiding those big fights,” Schale said. “He’s a guy who leans in really hard on issues that are important to the state.”

Scott, meanwhile, rode into office on the Tea Party wave, railing against Obamacare. He seemed for all appearances an ideologue, famously rejecting money for a high-speed rail from the Obama administration, to the chagrin of even some Republicans in his state.

But over the years, he has moderated himself. He has become almost comically on message, refusing to talk about anything except for jobs and the economy and a few other pet issues he picks every legislative session, like raises for teachers. The thrust of his 2018 campaign message has been the 1.6 million jobs created while he’s been governor.

“In the beginning, similar to but not the same as Trump, he had the CEO syndrome,” Stipanovich said. But “he’s gotten better at doing the job. Fewer gaffes, fewer unforced errors, more discipline.”

More recently, after the Parkland high school shooting that killed 17 people, Scott defied the National Rifle Association and got some modest gun control measures passed in a state that had been to date one of the most gun-friendly in the country. People from both parties commended how the governor handled that crisis. “Scott was actually pretty active in that fight,” Schale said. “He was the first governor to stand up to the NRA.”

But Democrats will “make sure Nelson has everything he needs because you can’t go forward if you go backward first,” Schale said. “It’s hard to imagine a scenario where we win the Senate without winning Florida.”

The governor’s campaign is also a wild card, with exciting young Democrat Andrew Gillum polling notably better than Nelson in his race against Republican Ron DeSantis. If enthusiasm for Gillum, the first black candidate for governor ever in Florida history, drives strong Democratic turnout, that would be a boon for Nelson’s chances.

But, ultimately, the race is likely to be determined most by Trump.

How Donald Trump will shape the 2018 Florida Senate campaign

Trump won Florida by 100,000 votes in 2016. The state remains divided on the president: Morning Consult reported in July that 50 percent of Floridians approved of Trump and 46 percent disapproved.

Once upon a time, Scott was one of Trump’s biggest fans. He chaired a pro-Trump Super PAC, endorsed the future president in a laudatory USA Today op-ed well before most GOP politicians were doing the same, and spoke at the Republican National Convention. Trump has been one of the biggest boosters of Scott’s potential candidacy, and his administration hasn’t hesitated to bestow some favors on Scott, like rolling back an unpopular plan to allow oil drilling off the state’s shores.

Lately, Scott has tried to put a little distance between himself and the president, notably condemning Trump’s racist “shithole” comments regarding African nations and criticizing the offshore drilling plan. He also opposed the Trump administration’s family separations policy during the crisis at the Mexican border; Florida has a large bloc of Hispanic voters.

“This is a conundrum faced by Republicans everywhere: Can Rick Scott get far enough away from Donald Trump to survive a competitive campaign?” Stipanovich said. “More recently, he is much less likely to embrace Trump publicly on some issue. He’ll bob and weave and obfuscate. That’s telling in itself.”

“A year ago, he could not wait to wrap himself around Donald Trump,” Stipanovich noted.