The explosion of 2020 political fundraising and interest by outside groups such as those backed by Michael Bloomberg and George Soros could push spending past $10 billion, more than the total GDP of several nations, including Rwanda, Guam, and Haiti.

At $10 billion, 2020 would be the most expensive race in U.S. history, easily topping the $6.8 billion spent in 2016, according to the Center for Responsive Politics.