Unfortunately that's just the reality of how people think. The person who is making confident declarations is going to come across as stronger and more inspirin

Unfortunately that's just the reality of how people think. The person who is making confident declarations is going to come across as stronger and more inspiring than the person who is being careful and thoughtful, no matter who is actually correct. It's not really a liberal or conservative thing, either. Someone making a passionate progressive speech is going to appeal to those inclined that way more than someone making a careful, nuanced progressive argument. Politicians know this and so will always hedge towards appearing decisive and "strong".