TALLAHASSEE, Fla. — Setting the stage for an expensive race that could help decide control of the Senate, Republican Gov. Rick Scott announced Monday that he's running to unseat Florida's Democratic Sen. Bill Nelson.

Scott, a friend and ally of President Donald Trump who is being term-limited out of office after eight years as governor, said he's now aiming for the Senate because "career politicians" have created gridlock and dysfunction in the federal government.

"Washington is a disaster," said Scott, who called for congressional term limits during his brief campaign kickoff at an Orlando construction company. "We shouldn't be sending the same kind of people to Washington."

Scott's entry poses a formidable challenge to Nelson, who has not had a serious challenge since winning his first term in 2000. Scott is a multi-millionaire businessman whose popularity has climbed during his final months in office, despite his sometimes rocky relationship with the Republican-controlled Florida Legislature.

"I don't care who is an opponent," Nelson said in Washington. "I always take them seriously, and I run like there's no tomorrow. And I think in this case a lot of the differences between the two of us are going to come out in the course of the campaign, so that's what I'd say at this point."

But Scott's connection to Trump could become a flashpoint in the battleground state.

Trump won Florida in the presidential election two years ago, but President Barack Obama carried the state in the two previous elections. Scott edged out narrow victories in his two runs for governor, both of them amid a backlash to Obama. A Quinnipiac University poll of Florida voters in late February found that Trump had only a 42 percent approval rating.

When asked whether he would ask Trump to campaign for him, Scott told Fox News he has not talked to the president recently about the race. Nelson went on the cable channel as well and immediately dinged the governor.

"He's not mentioned Trump at all, he's trying to keep his distance," Nelson said.

Democratic political strategist Steve Schale predicted the race would be close and that Trump's popularity could play a role.

"If those last few points are driven - just as they have been in the last 3 midterms - by voters seeking to use the election to send a message to the president, I think it will be very hard to overcome for Scott."

During his campaign speech, Scott cited the turnaround in Florida's economy during his time in office. The National Republican Senatorial Committee launched a digital ad Monday that goes after Democrats such as Nelson who voted against the tax bill approved by Congress late last year.

Democrats, meanwhile, have been anticipating Scott's campaign for months and have already ramped up their criticism, noting that Scott was forced out as chief executive of Columbia/HCA amid a federal fraud investigation. Although Scott was never charged with any wrongdoing, the health care conglomerate paid a then-record $1.7 billion fine for Medicare fraud.

Democrats also plan to fault Scott over his wealth and his record while governor, including his initial push for deep budget cuts to education and his back-and-forth position on whether to expand Medicaid.

Gun violence is also likely to be a major issue in the campaign.

Scott's record on gun laws earned him an A+ rating from the National Rifle Association before the killings of 17 people at a Florida high school this year. Ultimately, Scott signed Florida's new law raising the age limit to purchase rifles to 21 and creating a new process enabling law-enforcement to seize guns from someone who is considered a danger.

Scott contends Nelson has "done nothing" in the Senate on high-profile issues such as gun violence. Nelson said Scott has not done enough - he wants universal background checks and a ban on certain types of semi-automatic rifles.

Nelson began his political career in the era when Democrats controlled Florida government. He flew on a space shuttle as a member of Congress, and was elected as Florida's insurance commissioner before running for the Senate. His only notable election loss came in 1990 when he lost a Democratic primary for governor.

When Scott first entered politics, he appeared anxious with crowds and was an awkward speaker. Now, he's much more relaxed and self-assured. "I will bust my butt to win this election," he said.