Should Democrats be concerned about maintaining their margins in urban centers?

[Interlocutor is just not there yet]

One thing I'm surprised more people are talking about is how despite many suburbs swinging hard left, many city centers like Philadelphia, New York, Chicago, Dallas, LA, ect, ect swung right. For the most part, these cities are so one sided that only winning a district 80-20 as opposed to 90-10 isn't going to make a difference, but if the GOP can continue to make gains in these city centers as Trump did, it might cancel out some of the suburban trend, and could potentially bring states like NY and IL into play down the road. What do you think?

I think you just answered your own question.

Not to mention, Trump's percents in LA & San Francisco were the 2nd worst for a Republican in 104 years, next to his 2016 performance.

Or that Trump percents in San Diego, Orange & Riverside Counties were the 4th worst for a Republican since 1912.

But yeah, California Democrats oughta be scared sh*tless

[Interlocutor is just not there yet]

The only ways in which Democrats can win much of anything is to win the giant cities such as Detroit, Milwaukee, and Philadelphia. Or maybe Atlanta, Austin, Charlotte, Dallas-Fort Worth, El Paso, Houston, Miami, Phoenix, San Antonio, Tampa-Saint Pete.

Face it: they couldn't win Illinois without Greater Chicago, Minnesota without winning big in Minneapolis-St. Paul, Nevada without Greater Las Vegas, or Washington without Seattle. If they ever win Ohio again it will be because such cities on life support as Cleveland, Cincinnati, and Toledo get some vitality back.  

"The only ways in which Democrats can win most of anything is to win the areas which make up a significant chunk of a states population"