It's self-serving for outgoing GOP House members to blame their historic defeat exclusively on Trump. Of course that's a factor, but the factor they won't reckon with -- arguably the bigger one -- is their failed governance and unpopular policy agendahttps://www.nytimes.com/2018/12/02/us/politics/republicans-midterms-house-losses.html …
You could attribute it to a wide variety of factors, but not "population growth" in the sense you suggested.