But the cuts have done little to bolster the economy or the working class. In fact, incomes have stagnated, and workers have been forced to part with a larger share of their pretax earnings in the form of payroll taxes.

Meanwhile, where are the political champions of poor Americans? Whoever they are, they haven’t been producing results. Wages for the poorest have languished, partly because Congress has been so slow to raise the minimum wage — $7.25 an hour since 2009 — that its purchasing power is now about 10 percent less than it was in 1968. Lawmakers and conservative judges have also undermined workers by making it harder for them to unionize, so they are not in a position to demand better pay and better working conditions.

This tax bill would exacerbate all these trends. The Urban-Brookings Tax Policy Center and the Joint Committee on Taxation, both respected, both nonideological, say the bill would primarily benefit the wealthy and would leave most poor and middle-class Americans worse off over the long run. That’s without Congress doing anything else to widen the gap. But even now, Mr. Trump and Republicans in Congress are talking about cutting government programs like Medicare, Medicaid and Social Security next year to help make up for the more than $1 trillion the tax bill would add to the federal deficit.

Inequality in America does not have to be self-perpetuating. When people turn up at the polls, as they did recently in Alabama, they can produce unexpected results. That’s why Republican lawmakers might want to think again about whether they want to be the means through which their wealthy donors pull off this heist.