by 2040 or so ... 30 percent [of Americans] will choose 70 senators

--- Norm Ornstein, in a tweet on July 10, 2018

Tweet text:

I want to repeat a statistic I use in every talk: by 2040 or so, 70 percent of Americans will live in 15 states. Meaning 30 percent will choose 70 senators. And the 30% will be older, whiter, more rural, more male than the 70 percent. Unsettling to say the least

According to Jason Devaney in Newsmax quoting the Washington Post, the claim is supported by a 2016 population study by the Weldon Cooper Center for Public Service of the University of Virginia.