How both sides can believe they are losing

If you read narratives of recent history from the perspective of the left and the right, each side believes it is losing. One could dismiss this as marketing strategy. If our side is winning, then why is it urgent to read my book or donate to my organization?

But I think it is possible for the each side to sincerely believe it is losing.

The left presumes that government can solve problems. We have problems. Therefore, we must be losing!

The right presumes that the government causes problems. We have problems. Therefore, we must be losing!

That is from Arnold Kling.