a baseless claim
If the economy had nose-dived in 2017, there’s no doubt the media would have pounced on Trump policies as disgraceful failures. But with the economy red-hot, he gets little credit. That’s a double standard.
The author is accusing the media of a double standard based on pure speculation of how they might have reacted in a hypothetical scenario. There is no basis for this claim other than the author's imagination.