But the Democrats weren't obligated to debate. I'd suggest it's far more likely this is a feint to cause Trump to focus his attention on a distraction while the cabal prepares to trot out it's real candidate at a later period, now with the support of the party faithful who are worried about Biden. If you just show up at the convention and replace him you'll tick off his supporters, but if you allow him to look week and feeble you cause those people to seek alternatives which you provide.