This type of things has happened countless of times and this is the first time I have seen him defend Obama. Usually he smiles uncomfortably and that's all.
I agree with 12thMan but I'll give him props for doing more than simply smiling uncomfortably. In recent McCain/Palin rallies people screamed "terrorist" and "kill him" when Obama's name was mentioned and they referred to him using his middle name to "work the crowd" so I think overall McCain "sticking up" for Obama is "too little to late." Playing the good guy is not going to help McCain's defunct campaign.