I went to a bike shop and bought a wrench, tire levers, a new tube and a patch kit (for the future). It turned out that the tube had a new hole in it and my patch had not failed. I just replaced the tube anyway and it’s working fine for the moment. I’m a little concerned that the rim, which is out of true and maybe out of round also, is causing the tube to puncture, but I don’t know enough about bicycles to know how likely that is. I’ll probably replace it anyway with one of the rims I have in the basement. They will probably be in better condition.