President Trump's base has gotten smaller.
That's a key finding of an analysis of how the U.S. electorate has changed since 2016, based on census data analyzed by the Brookings Institution and NPR.
In 2016, Trump was helped to victory by winning a record margin among white voters without a college degree. But in the last four years, they have declined as a share of the voting-eligible population across the U.S. and in states critical to the presidential election. Nationally, the group has gone from 45% of eligible voters to 41%.