Florida Gov. Rick Scott (R), a close ally of President Trump, formally entered the race for a U.S. Senate seat on Monday, kicking off a marquee contest against Sen. Bill Nelson (D-Fla.) that has major implications for control of the Senate next year.

Scott made the announcement in a video distributed on Twitter, framing himself as an outsider to a “horribly dysfunctional” Washington — a theme he repeated to a group of supporters in Orlando minutes later.

“Washington is full of old thinking,” Scott said. “Washington is tired. And the truth is, both political parties share some of the blame.”

Scott’s announcement sets the stage for what is expected to be one of the most expensive races in the country, taking place in a swing state that was a key to Trump’s 2016 victory. It also offers a test of whether a tight alliance with Trump provides more help or harm in the current political environment.

For months, Trump and Republican Party leaders have been trying to coax Scott to challenge Nelson, who is seeking his fourth term and has been stepping up appearances across Florida, the nation’s third most populous state.

Florida Gov. Rick Scott interacts with people at a restaurant in Doral, Fla, last month. (Joe Raedle/Getty Images)

[Fla. Gov. Rick Scott expected in Washington to raise money for widely anticipated Senate run]

Scott, a two-term governor, has been preparing for a campaign for weeks, huddling with donors and building a campaign team. This will be his first run for federal office for the 65-year-old who made a personal fortune as a health-care executive.

In his remarks in Orlando, at a construction firm in the city, Scott called for term limits for Congress and said that in Florida’s capital, he never really fit in as a businessman. The same would be true in Washington, Scott said.

“We don’t need any more talkers in Washington, we need some doers,” he said.

Nelson is expected to highlight Scott’s ties to Trump in a state Trump only narrowly carried over Democrat Hillary Clinton.

Scott was an early cheerleader for Trump — he led a super PAC that supported Trump’s bid — and Trump has been publicly twisting Scott’s arm to run for the Senate for months.

That included during a September visit by Trump to Florida to survey hurricane damage. After praising Scott for doing an “incredible job” as governor, the president added: “I hope this man right here, Rick Scott, runs for the Senate.”

In an interview Sunday with Politico, Scott pushed back when asked if he considers himself a “Donald Trump Republican.”

“I consider myself Rick Scott,” Scott said. “I don’t consider myself any type of anything. … I run on what I believe in. I’ve been very clear. People ask me that a bunch of times, about ‘Are you this or are you that?’ No. I’m Rick Scott. I grew up poor. I believe in jobs.”

Nelson, a former astronaut, is a political veteran, having also served for more than a decade in the U.S. House and as state treasurer, insurance commissioner and fire marshal in Florida. While mostly aligning with his party on major issues, Nelson has also sought to appeal to centrist voters by working with Republicans. Last year, he collaborated with Sen. Susan Collins (R-Maine) on a health insurance measure.

On Monday, Nelson, who is the top Democrat on the Senate Commerce committee, was planning to meet with Mark Zuckerberg, a day before the Facebook chief executive officer is scheduled to testify to the panel about privacy issues.

During an appearance last month in Florida, Nelson said he was ready for a challenge by Scott.

“It’s going to be clearly a set of contrasts on so many issues, from the environment to sea level rise to oil drilling off the coast, to the expansion of Medicaid in Florida,” Nelson told reporters. “I mean the list just goes on and on and on.”

Democrats are planning to cast Scott as an out of touch politician only interested in himself.

“Rick Scott has spent seven years ignoring Florida’s middle class, while enriching himself and his political cronies by millions of dollars,” said Joshua Karp, a spokesman for American Bridge, a super PAC that promotes Democratic candidates.

The Democratic Senatorial Campaign Committee, which has been gearing up for a possible Scott bid for months, last week hit on the same theme, debuting a “Self-Serving Scott” website that claims “Rick Scott is a self-serving politician who will say and do anything to help himself at Floridians’ expense.”

Less than two hours before Scott’s announcement on Monday, the DSCC also circulated a 2015 editorial from the Tampa Bay Times that referred to Scott as “the state’s worst governor in the last half-century” after he declined to take Medicaid expansion funding.

Guns could emerge as a central issue in the campaign. Weeks after the deadly mass shooting at a Florida high school in February, Scott signed new gun regulations into law, defying the National Rifle Association.

His decision could boost his appeal to centrist and Democratic voters who have been very vocal about wanting new gun control. It could also alienate him from conservative gun owners who do not like to see new restrictions on firearms.

While Scott and Trump have differed on guns, immigration and several others issues, they are widely seen as tightly aligned, as Scott has been a frequent guest at the White House and Mar-a-Lago, the president’s estate in Palm Beach.

Scott’s close relationship with Trump was also highlighted in January, when the administration agreed to rule out oil and gas drilling off Florida’s coast after Scott voiced strong opposition. The announcement came shortly after Interior Secretary Ryan Zinke had moved to allow new drilling in nearly all United States coastal waters.

One emerging complication for Scott is his relationship with Sen. Marco Rubio (R-Fla.). While Rubio has said he supports Scott’s campaign, the two have a difficult past that has flared in recent weeks. Rubio has also said nice things about Nelson, irking some of the governor’s allies.

Following Scott’s announcement on Monday, Rubio took to Twitter to voice his support for Scott, saying “one of the most important roles” of the Senate is confirming federal judges — a task made easier with a Republican majority.

Next week, Scott, who is term-limited in his current post, is expected to travel to Washington to raise money for his campaign, according to three Republicans familiar with his plans.

Party power brokers have been in contact in recent days to make arrangements for Scott’s trip. The Republicans said Scott is expected to be in Washington on April 19. They spoke on the condition of anonymity to describe plans that had not been announced publicly.

There has been talk among Scott’s close associates about amassing more than $100 million for his bid. Scott can put his own money into the campaign, but those close to him say he will rely most heavily on funding from donors.

Following his appearance in Orlando on Monday morning, Scott was scheduled to a attend an afternoon event at a citrus packing house in Fort Myers.