It wasn't so much that he was seen as a "has been". More of a trouble maker, given to switching parties if the one he was currently in didn't have a policy set he approved of.
You can view that either as his being a 'chancer', lacking loyalty, or as being a man welded to his own principles. I prefer the latter, more admirable, view. He switched parties several times, sitting with all three in the end; each time was on a clash of principle with those 'above' him.
I don't mind much people who switch befre the election, but the turncoats who do it after annoy me. The people who voted them in in all likelyhood would have never done so...