30%. Dawson should be a heavy favorite as long as he is sensible and doesn't try anything stupid like proving he can take a shot.
I give him the slim chance of 10-15%. Dawson is too fast, moves to well, and has a great offensive arsenal. Tarver can only win, if Dawson makes youthful mistakes, and therefore gets himself knocked out. Tarver can't win on pts, and can't control the match. Milk duds demise as a top boxer has begun long ago...
Before the Johnson fight, I would have said 25%, but after that gift victory, I will say between 40-50%. I favor Dawson slightly, but this is either man's fight.