If almost all who believe he violated ethics already thought his performance was poor, their new belief about his violations wouldn’t change the percent who judge his performance good/excellent. Their opinions weren’t going from good/excellent to poor; they were already poor.

If this has any effect, it makes the discrepancy harder to explain. On top of the ethics violations, people’s opinion about Walker’s opponents is now more positive. So why would opinion about Walker’s performance not become more negative?

We already know about half believe Walker violated ethics. The 20% who weren’t aware of the accusations could be among the people who don’t believe he violated ethics. This doesn’t add information that could explain why opinion about Walker’s performance hasn’t declined.

This doesn’t help explain how opinion about Walker’s performance hasn’t declined. If anything, we’d expect activities from anticorruption groups to negatively affect opinion about Walker’s performance.

Walker’s argument in his defense doesn’t explain why opinion about his performance hasn’t declined. We don’t have any reason to think people believe his defense or that his defense would cause people to give less weight to the violations when judging his performance as mayor.