Just a terrible terrible night for Rubio.
In the first half of the debate he went full-on Macro Robot. Then in the second half of the debate he was visibly sweating buckets in glorious HD. The rest of the candidates were dry as a bone, so he can't chalk it up to hot stage lights. It literally looked like Rubio's circuit boards were overheating, which was causing his synthetic skin to melt.
If I was a Republican I would be concerned that he would literally explode if he got in a debate with Hilary Clinton. One of the key attributes of an establishment candidate is the ability to at least hold their own in the presidential debates. After tonight, Rubio now appears as a political lightweight who has trouble thinking on his feet.