There's still some confusion about this. Ford is the incumbent. He has as close to 100% name recognition and voter awareness as any politician can possibly attain. Short of people who have particular mental illnesses or who purposely avoid all news, it's difficult to imagine any potential voters in the city who aren't aware of Ford and have some opinion on him.
The challengers are just that: Challengers. Unknown, untried. That at least two of them (I'm assuming Chow will challenge) can already beat Ford in match ups even with multiple other vote-splitting candidates left in, is very bad news for an incumbent.
Basically, voters have already decided against Ford, they just haven't yet finalized who they want to replace him with. That means the initiative in the campaign is all with the challengers. It almost doesn't matter what Ford does or says. Everyone knows him, almost nothing he does now will change many minds about him (hence desperate stunts like going on Kimmel). But the challengers can either make or break themselves in the campaign. If they all manage to break themselves, Ford can possibly be re-elected with some kind of plurality vote (I'm prepared to predict he cannot get a popular vote majority). If.
This is a terrible position to be in as the incumbent. It is not hopeless, defeat is not certain, but his victory is dependent on several others failing.