Bull premise. Considering we're already deep in the red, any additional spending goes into the national credit card, which we will have to pay for at some point, but will include interest. It's very likely this $800+ billion will cost us well upwards of 1 trillion once you add up said interest.
Not once, ever, tax cuts have paid for themselves in the form of recouped revenue due to growth. Not once. This is not going to be the exception unfortunately. This is really no different than a $1 trillion 'stimulus package' on it's face.