From an outsider's perspective, "bubble" isn't an accurate descriptor for either group. I find more sense in articles that describe two (or more) significant-minority factions speaking entirely different languages.

http://www.theatlantic.com/politics/archive/2016/07/why-demo...

http://www.vox.com/2014/9/15/6131919/democrats-and-republica...

http://www.csmonitor.com/USA/Politics/2016/0407/Why-Democrat...