Sure, Republicans say this, but did we think that they would say that they expect their tax plan to increase the debt by $1.5 trillion, but rich people need tax cuts? Given their endless tirades about deficits under President Obama, Republicans are pretty much required to say that their tax cuts will pay for themselves regardless of what they actually believe.
So why don't we recognize this very simple fact and stop telling people what Republicans believe, as this NYT article does?
"But the bill’s passage was made possible by a near-complete Republican embrace of the idea that about $1.5 trillion of tax cuts will pay for themselves, by producing enough economic growth and additional federal revenue to offset their costs to the Treasury.
"That belief was contradicted by several studies, including one from Congress’s official economic scorekeeper, which Republicans dismissed as overly pessimistic."
The NYT's reporters have no idea what Republican members of Congress believe about the fiscal impact of their tax cut, so they should not be implying that they do. As a practical matter, they may have no beliefs on the issue whatsoever. They get and keep their jobs by doing what their donors want them to do, not by thinking about the economic impact of the bills they pass.