I have a hot tip for Washington Post reporters: politicians aren't always honest. As a result when they say they believe something, it doesn't mean they really believe it.
This means that the Washington Post likely misled its readers in a discussion of Republican tax cut proposals when it told them:
"Republicans believe the corporate rate cut and other incentives will stimulate economic growth, offsetting the revenue loss."
The reality is the Washington Post's reporters have no clue what the Republicans pushing tax cuts really believe about the impact of tax cuts on growth. If these Republicans were at all familiar with with the evidence, they would not expect their tax cuts to have much, if any, positive impact on growth.
So while it is possible that Republicans believe in something that is not true, it is possible that they are deliberately deceiving the public. It is also possible that they have no clue whatsoever about the impact of tax cuts on the economy, just as they have no clue about the impact of their health care proposals. They are simply voting as their funders are telling them to.
Newspapers are supposed to report the facts, not make them up, as the Post is doing here.