Attacks on an opponent’s character should be avoided in political debates.
Conclusion (should)
Attacks on an opponent's character should be avoided in political debates.
Evidence
Attacks on an opponent's character don't confront the argument, and they cast doub on the opponent's moral right to be in the debate at all.
Evaluate
For Strengthen+Principle questions, we have a very predictable pre-phrasing goal of just saying "IF Premise, THEN Conclusion".
If there are multiple premise ideas, as there are here, any one of them can be used as a launching pad that gets us to the landing zone of the Conclusion.
Goal
Let's look for either of these,
if something does not then should be not confront the → avoided in opponent's argument political debates
if something casts doubt then should be on opponent's moral → avoided in right to be in debate political debates