Scott, a two-term governor, has been preparing for a campaign for weeks, huddling with donors and building a campaign team. He said Washington is "horribly dysfunctional", and the change starts in Florida.
"We need to shake up Washington", he told supporters at the warehouse.
In a memo sent to reporters Monday morning, Democratic Senatorial Campaign Committee executive director Mindy Myers called Scott "self-serving and dishonest" saying he is "looking out for himself at Floridians' expense".
The Democrats have shown some fear in Scott as they've spent a long time preparing for his announcement. The National Republican Senate Committee followed with an ad bashing all Democrats, including Nelson, for voting against the tax-cut bill past year.
Scott repeatedly talked up his "outsider" status. His first budget proposed a big reduction in K-12 education spending, and he immediately worked to repeal environmental protection measures, gutting the state's growth management regulations. Critics say one of his misses was environmental issues along with Medicaid.
Democratic political strategist Steve Schale predicted the race would be close and that Trump's popularity could play a role. "I'm going to run to win", Scott said. She traveled with Scott on his South Florida trips and was particularly visible in the aftermath of Hurricanes Irma and Maria, and was at his side after the deadly shootings at Pulse and Parkland.
Instead, Scott focused on how the state helped Puerto Rico in the wake of Hurricane Maria which ravaged the island a year ago.
"Now we've got to take that same mission to D.C.", Scott said.
Puerto Rican native Raymond Hernandez, a 51-year-old Orlando pastor, attended Scott's rally.More news: Iran Threatens Israel in Excess of Air Strike in Syria
Jereima "Jeri" Bustamante, 33, press secretary to Gov. Rick Scott since 2014, died Sunday evening after the boat she was riding in crashed into a stand of mangroves in a narrow channel off Islamorada.
Republicans consider Mr. Scott, with his personal wealth and broad name recognition, the only candidate with a shot at ousting Mr. Nelson given Florida's size and expensive media markets. It has helped boost his image. In the same survey, 42 percent of voters said they approved of Trump, while 54 percent said they disapprove. The most recent Mason-Dixon poll giving Scott a 1 point lead with 11 percent still undecided. Last year, he collaborated with Sen. The same would be true in Washington, Scott said.
One emerging complication for Scott is his relationship with Sen.
Retired Winter Garden teacher Vivian Lyte-Johnson, 71, stood outside Scott's campaign kickoff event with a sign slamming Scott as a "do nothing" Republican.
In his remarks, Scott took credit for reversing the state's high unemployment rate since taking office during the recession.
Much will depend on the strength of populism in this midterm cycle. "I will bust my butt to win this election", he said.
Scott held his kickoff in a back storage area behind ODC's offices. "We do that in this state". Nelson said Scott has not done enough - he wants universal background checks and a ban on certain types of semi-automatic rifles.
His announcement was a preview of expected attacks against Nelson, a three-term incumbent who previously served in the U.S. House, the state Legislature and in Cabinet-level elected positions in state government during a career that spans more than four decades.
Political experts are expecting a tight race.