A reader raises another point I should have mentioned:

Even more critical was Reagan going back on his tax cuts, agreeing to TEFRA in Aug-Sept of 1982. I was working for local GOP state house races in western Pennsylvania, and we had competitive candidate and enthusiastic campaigns in all kinds of places where there had never been any, such as heavy union districts in the Monongehela River valley. Even though times were tough, and Reagan had fired the PATCO members who went on strike, the campaigns were active and enthusiastic. But these campaigns went totally flat after TEFRA. I still remember one candidate asking me what he was supposed to tell voters, who asked him what the difference was between the parties. He was absolutely crushed by Reagan agreeing to raise taxes.