I’m not saying that Republicans couldn’t still do a comprehensive and permanent tax reform in theory. Set health care aside entirely and there are still lots of clever and plausible ways to overhaul and improve the tax code without sacrificing revenue.
You could cap various perverse deductions that mostly benefit wealthy blue-state taxpayers, like the home-mortgage and state and local tax deductions, and use the savings to lower rates across the board. You could cut the corporate tax rate and raise the capital-gains tax rate to compensate, as Senator Mike Lee has proposed. You could even (gasp, heresy, gasp) raise the top income tax rate, as Steve Bannon reportedly wants to do, and use the savings to cut payroll taxes or fund a new child tax credit.
But Republicans don’t seem equipped to pull off anything complicated, they don’t look united enough to take political risks, and they aren’t ideologically ready to pass anything heretical. So barring a sudden transformation in the party and its leadership, a temporary, deficit-financed tax cut is the only thing that has a decent chance of happening.