Don't agree. The public has come to expect debates. Reagan was in a stronger position than Bush is now, and he nevertheless debated twice.
Jimmuh Carter initially refused to debate Reagan, then dragged his feet until public opinion finally forced him to capitulate... there was one debate in the final week of the campaign... and Jimmuh got his clock cleaned by Reagan... and the rest is history.
So I'd say, agree to debates, just make sure they're not too close to the election so any positive effects have time to wear off, in the unlikely even K does well.
"There you go again!"