The incident can best be understood through a series of four still photos captured from the security video:
Again, this is not a brutal mugging. But it certainly is an act of physical, unprovoked aggression that should not be tolerated. A judge or jury will have the final say, but a charge of misdemeanor battery seems perfectly appropriate.
At the very least, Lewandowski should publicly apologize for his behavior, and Trump should apologize as well for the aspersions that he has cast on Fields' character and veracity in the aftermath. But we all know that's not going to happen. That would require a modicum of class and a capacity to feel shame, and Trump is capable of neither.
Any doubt about that fact was eliminated in a Trump press conference this afternoon. "How do you know those bruises weren't there before?", he asked in defending Lewandowski.