It could be as simple as bringing a CV positive individual(s) into the mix, have them cough/gag on the podium prior to the debate or mingle with Trump's team. Exposure may have occurred earlier, at ACB's SC intro too. I think Q planned this, denied the DS an opportunity to expose Trump to CV until the debate, gave the Dems the opening knowing they would take it. The same could be said about the SC intro with ACB, retribution for announcing RBGs death (that they were hiding for later) creating an opening for ACB to become her replacement ... at the SC intro presser.