[Cboldt]

Imus: Is there anything in your past that will derail your campaign? In particular, is there any truth to the Drudge report?

Kerry: None. You can continue to support me.

That was the extent of the discussion.

[RippleFire]

Which means he can't issue a flat denial.

[Jackie-O]

Kerry probably only agreed to make his appearance today with the stipulation that the topic only be brushed upon, and then swiftly brushed off. I'm sure Kerry realizes that the question had to be asked so he allowed Imus to ask.
He will stay in denial until some hard evidence comes to light ala Lewinski-gate, or the girl comes foreword and admits to an affair.