Yeah, all poliitcal bullshit aside, something seems wrong there.
He doesn't fall, he doesn't even sway, he just goes catatonic. He clearly hears her talking, but can barely respond and only his eyes move towards her.
Maybe some kind of siezure. Scary for sure.
Last time he left the podium and came back out later and answered more questions, so I just don't know what to make of it.