PITTSBURGH — If you wanted to have a keen, dispassionate understanding of how much the Republican Party has changed over the past eight years, all you had to do was stand outside the PPG Paints Arena in the city’s Hill District neighborhood and see the line of people stretched 10 blocks in either direction up Fifth Avenue.

The attendees were young, male and female, and diverse. There were black, white, Hispanic, and Asian people all having a great time, getting to know each other, singing songs in line, swapping stories of where they were from, and almost always finding out they shared a mutual friend.