The House districts with the closest races in the midterm elections tend to be more educated than the rest of the country. Of the 30 districts currently rated as "tossups" by Cook Political Report, two thirds have a higher prevalence of college degrees than the national average.

Why it matters: It's yet another sign of potential midterm trouble for Republicans, since 28 of those races have a Republican incumbent and President Trump did best with people without college degrees. Strategists from both parties think it'll come down to how suburban voters react to Trump.

The backstory: A Pew survey in March 2018 showed that Trump's approval was highest among those who had never been to college, and a FiveThirtyEight analysis in November 2016 found that Hillary Clinton excelled in higher-educated counties.

What they're saying: