At this point, many life-long Republicans are struggling to understand why their party left them. I think it started when the Dixiecrats joined the party 50 years ago over the Civil Rights Act. While welcoming those politicians and their voters seemed like a good idea at the time, those Republicans were actually joining with people who had for generations opposed what the party of Lincoln had been founded on.
Since then, the Republican Party has been a coalition of true conservatives, evangelicals, corporate power, and the crowd that has taken it over now. I'm not really clear on whether Trump has won over a number of Republicans because they are so anti-Hillary/anti-Democrat, or because he appeals to them with his authoritarian macho rhetoric. Or both.
The fact remains that were my parents alive today I don't know what party they would be in, but it isn't the one I see today.