Democrats' Senate math problem

CNN reports:

Democrats are defending a whopping 25 seats as compared to just eight for Republicans. But it gets worse -- much worse -- for Democrats.

Of their 25 seats, 10 of them are in states that Donald Trump won in the 2016 presidential election. Five of those 10 -- North Dakota, Missouri, Montana, West Virginia and Indiana -- are states Trump carried by double digits. By contrast, only one Republican -- Dean Heller of Nevada -- represents a state that Hillary Clinton won last November. Only one other Republican-held state -- Arizona -- was even marginally competitive in the presidential contest.

The struggles of the Democrat party.