I did hear him spit out excess saliva during the speech. it does look like Vaseline though to be honest
I suspect you are right. Probably had Vaseline or something for chapped lips and might have wiped it off just before getting to the podium except he missed the corners of his mouth. When he takes a shower, I wonder if he has to have someone yell outside the bathroom "Did you remember to wash behind your ears?" Sheesh... that was disgustingly amateurish, even for a DemonRat.