Political leader: In this political dispute, our side will benefit from showing a desire to compromise with the opposition.
Conclusion
Our side will benefit from showing a desire to compromise with the opposition.
Evidence
If they respond positively, a compromise will be reached.
If they don't respond positively, they will be held responsible for the failure to compromise and our side will benefit.
Evaluate
We have to prove that showing a desire to compromise will "benefit our side", but we're given two different (binary, exhaustive) possibilities for what might happen if we show a desire.
To guarantee the conclusion, we need to make sure that our side benefits no matter what.
We know that if they don't respond positively, they get blamed and we benefit (it said so explicitly).
But we don't know that we benefit if they respond positively. We only know that a compromise will be reached.
Goal
The only loose end in guaranteeing that we benefit is establishing that .