I never really saw either camp as smug, just having a lot of conviction and scared that the other side winning means the demise of America. I think trump supporters have more conviction, but Biden supporters have more clarity and wherewithall about their opinions which counts for something. Probably whoever has the strongest side/the highground in debates will appear smug just because they have the luxury of being right, rather than just being full of crude, stupid passion/hot air, lies and misapprehensions, which is why Democrats have the reputation of being smug.