You've already established the secret banker cabal defense. I don't think "Boo Donald" is a realistic option.
You're incorrectly assuming there's only one issue that could be a point of contention, and it's still possible that the economy won't perform well because of bad GOP policy.
The "banker cabal" might be "secret", but the fact that it raises interest rates can't be; if they do not raise interest rates or even lower them, and the economy performs poorly, and there isn't some catastrophe, then the GOP has no excuse, but if they do raise interest rates, then the GOP does have an excuse.
There are issues unrelated to the performance of the economy that cannot be blamed on the banksters.
For example, if the US decides to provide Israel with a bunch of help with fighting their war and supporting their genocide of Palestinians, then the GOP would be squarely responsible for that - especially if it drags the US into getting directly attacked in a war.
If the GOP creates laws that are anti Bill of Rights, such as censorship laws or laws imposing religion, contrary to separation of church and state, then the GOP would be squarely responsible for that.
There's plenty of other ways, that have nothing to do with the banksters.