Any party can win if it gets the majority of candidates across all parliamentary constituencies. However, a Prime Minister must be elected as an MP somewhere. If Reform got a majority without Farage being elected, they would be in a strange situation where the leader of the party couldn't become the PM. It's amusing to think about, in a schadenfreudish way, but the chances of that are slim. He would certainly stand in a general election for the same seat, other major parties would contest it, and it seems that Clacton-on-Sea supports him over the others. This by-election is special because the major parties are boycotting it for being a self-serving stunt that it is.