The businessman-turned-politician had famously abandoned the Democratic Party in 2001 to run for mayor as a Republican — a switch he mostly made to enhance his then long-shot chances in a race that was crowded with left-leaning candidates in a historically blue city. After his surprise win, he went on to serve for three terms — engineering a one-time exception for himself to get around the two-term cap — and in 2007 he broke with the Republican Party to register as an independent.