However, when Trump said, "I hope you can let this go," Comey wasn't "too smart" at all.  Smart response:  Sorry, sir, not sure what you mean.  Can you clarify what you mean by "hope you can let this go?" And wait for Trump to incriminate himself, or, back off.  

Instead--like many of us do in moments of surprise or stress--Comey did NOT ask the question that needed asking.