But what makes him charismatic? I have heard others say it, but no one can quantify it.
With Obama, it's obvious: he's one of the world's greatest speakers, and can put together great speeches. Beto lacks both these traits, all I see of him is a struggle to put together a coherent 5 minute speech, and LOTS of rapid hand gestures, like he is trying to spoof Hitler.
He just extremely likeable, just like Obama was. He might not have Obama's speeching ability, but he actually did a good job against Cruz in debate. He will just need to control he hand gestures a bit better. But in the end, I don't think that will matter much.