What happens if Trump fails miserably as president?
Were 2 months in and he hasnt accomplished anything. What happens when there is no wall, no jobs coming back, etc and rural America continues to decline?
This is a big part of my opinion. How well Trump does will affect how these young people who are currently at least
open to Republicans behave politically in the future. If Trump bombs really bigly, whether it be through a recession and/or mass corruption, then he could completely stain the GOP's brand among these young kids. I'd argue that he is far more likely to do that than he is to "turn everything around" and make the GOP shine.
From a partisan perspective, I'm not overly concerned. If Republicans went from winning 36% of 18-29 year olds to winning 41%, it's not that big of a deal. That's why Democrats pulling such huge margins among these generation(s) is so damaging to the GOP. It makes it hard to recover.