Calling Washington “horribly dysfunctional,” Florida Gov. Rick Scott will challenge US Sen. Bill Nelson in an election that could be one of the most expensive and highly watched races in the nation.

The Republican governor will formally announce his campaign to unseat Florida’s only statewide-elected Democrat on Monday in Orlando. During his announcement, Scott is expected to criticize “career politicians” and call for term limits for members of Congress.

Scott is a multimillionaire who never ran for office before he ran for governor in 2010. He rode into office as part of the tea party movement and called for massive budget and tax cuts. But he was forced to scale back his plans amid opposition from the GOP-controlled Legislature. He also changed his hard-line positions on immigration.