Since then, his signature legislation has failed to pass as intended, he's broken a strike, he's supported a genocide, he's moved to the right on immigration, and he's claimed to have defeated Medicare. He's alienated his base and demonstrated that people who were fretting about his age might have been on to something after all.
He beat Trump in a nail-biting squeaker of a contest in 2020, and centrists have been pretending he's invincible ever since.