As a former member of the Republican Party, I have two words of advise for them in 2020... dump Trump. He is the reason I left the party in the first place, and I thought to myself, maybe the rest of the party will finally realize this man is a complete fool and support someone else in the 2020 race. But the complete opposite is happening and they will wish they hadn't done that.
Though it's a long way away, there are numerous statistics showing a decline in the opinion of the Republican Party as a whole. And as the Democratic Party didn't fare well either, they are holding steady as the GOP is crumbling. Mr. Trump, in my opinion, is the reason for this decline. Moderate Republicans and suburban voters alike are not your "Trump voter." They prefer a mainstream candidate with experience in public office and a temperament that is fit to serve. 2016 was the first time college educated white voters as a whole voted Democratic in what is typically a Republican leaning group. To my knowledge, Mitt Romney won them by nearly 12 points.
My point being, these groups are feeling alienated and do not support the populist and nationalist sentiment brought on by Trump. The GOP claim they made significant gains in blue collar voters, but yet they lost the demographic groups stated above. This is my point, you have to have a candidate who is a big tent or a one size fits all. If the GOP continue to support the principles Trump is pushing for, they can guarantee their losses among college educated whites and minorities is going to continue to grow, thus crumbling and fracturing an already tumultuous party.