I see a somewhat different picture. It seems to me that, in the age of negative partisanship, the GOP is making the best move they have.
First of all, Republicans now have a legislative victory, and nothing succeeds like success. While I cheekily suggested back in June that the GOP should do literally nothing rather than pursue any of its unpopular agenda, that was partly because I didn’t believe at the time that they were capable of passing a bill. But it’s obviously better to have a win than a loss. I’d expect the bill to become more popular with those who lean Republican now that it’s a win for their side.
Moreover, in notable contrast to the attempt to repeal ObamaCare, the tax cut has been sold primarily with an argument that is not obscenely contrary to fact. Repeal of ObamaCare was sold as something that would provide better health insurance more cheaply, which was not a remotely accurate description of any version of the bill. The core of the tax cut, on the other hand, is a huge reduction in corporate tax rates — and nobody has really tried to hide this.