I also get the sense that his "transit plan" might just (hopefully) turn out to be his jump-the-shark moment. As others have already mentioned, even many of his die-hard supporters are baffled by its sheer stupidity, and even journalists and media (the Sun) that have been kissing his ass since he announced his candidacy, are heavily criticizing him, since transit is the number one election issue. He has angered a lot of people with his negative, destructive attitude.
I'll even throw out my own stunning experience - my parents, who have blindly supported Ford since the start simply because he's not one of those "lefty whackos", were shocked by his joke of a transit plan, and much more surprisingly to me, were even offended by his ludicrous idea to kill the city's streetcars. And they're stereotypically conservative, suburban, pro-car folk who totally ignored all of his countless flaws before this whenever I tried to show them that he's not the kind of guy you want running the city, so if even they have gone cold on him, then there's hope after all.
On a related note, Dalton McGuinty stated yesterday that Transit City will continue to go forward exactly as planned, even if someone gets elected mayor who isn't in favour of it (naturally he didn't mention any names, but it was crystal clear who he meant.) If anything, I'd say the real threat to all the transit expansion that Toronto and the rest of the GTA desperately needs isn't Rob Ford, but rather Tim Hudak.