John Avlon : Mitt Romney 's VP selection is a gamble that changes the campaign . Comment: The opinions expressed in this commentary are solely those of John Avlon . Ryan 's focus on substance is a welcome change for a largely negative campaign , Avlon says .
John Avlon : Mitt Romney 's VP selection is a gamble that changes the campaign . Comment: Ryan 's focus on substance is a welcome change for a largely negative campaign , Avlon says .