Him dropping out wasn’t his biggest mistake. Him choosing to drop out months after the primary process was his biggest downfall. He basically fucked the democratic party because he couldn’t swallow his ego and drop out when it was clear his popularity among the country was dwindling even in the party itself. Every advisor he had said “hey you likely shouldn’t run again” but he stayed, Hell fucking Obama even told him “yo you aren’t going to win this”. His stubbornness to run for a second term is what killed the chances of a democratic win here.