This one demographic shift could doom Trump's 2020 campaign: elections expert
Donald Trump at a rally, photo by Gage Skidmore.

Polling has consistently shown that President Donald Trump's strongest base of support comes from white Americans who do not have a college degree -- but new analysis shows that they might not be enough to carry him across the finish line this year.

Writing at NBC News, Cook Political elections expert Dave Wasserman explains that "in 2020, noncollege whites are on track to make up about 43 percent of the nation's adult citizens, down from 46 percent in 2016."

It was Trump's strength with non-college whites in the Midwest that secured his victory in Pennsylvania, Wisconsin, and Michigan in 2016, and any decline in that demographic could easily tip those states back to Democrats.

"A new interactive collaboration by NBC News and The Cook Political Report finds that if 2016's rates of turnout and support were applied to 2020's new demographic realities, Trump would narrowly lose Florida, Michigan, Pennsylvania and Wisconsin -- more than enough to swing the presidency to Joe Biden," Wasserman explains. "And, Trump would lose the popular vote by about four points, roughly double his 2016 deficit."

None of this suggests that Biden has the election locked up, although Wasserman says that it will nonetheless be a greater challenge for Trump to pull off the same trick he pulled four years ago.

"Trump might need to boost noncollege white turnout by about 5 points -- from 55 percent to 60 percent nationally -- just to offset the impact of their dwindling share of the electorate and get back to the same 306 electoral votes he won in 2016," he writes.