Funny, that video shows exactly the opposite of what the Trump supporters say that it does. When the initial video came out, it showed Lewandowski moving toward Fields, but it wasn’t clear that he’d touched her. This video you linked shows clearly that she was moving in one direction and he grabbed her and her direction reversed immediately. That doesn’t happen from him tapping her on the arm - it’s because he grabbed her arm and pulled.
It looks more like she lost her balance or footing (maybe heels?) as the group moves past her.
It really doesn’t matter WHO grabbed her arm...A person reaching out with an object in their hand and touching a presidential candidate SHOULD get the h*ll knocked out of them...Remember Bobby Kennedy in ‘68????.....