Even without Rick Scott's money, history indicates the 2018 U.S. Senate race will be a very, very expensive affair.

When incumbent Democratic Sen. Bill Nelson first ran for the office in 2000, spending topped out at $19.3 million, according to a recap by opensecrets.org.

In the 2016 Florida Senate race won by Marco Rubio, spending hit $110.5 million.

That's a 472 percent increase in 16 years. And it illustrates the rise of outside spending. During the time, such spending increased from $2.4 million to $50.6 million.

Now comes millionaire Scott, who's expected to enter the race on April 9.