WASHINGTON — It’s a Christmas gift the middle class might want to give back in a few years.

The Republican tax overhaul bestows an initial infusion of cash on nearly every taxpayer next year. That extra income is likely to please millions of households, support consumer spending and perhaps give the economy a short-term lift.

Ordinary households should enjoy it while it lasts. Over the next several years, multiple analyses of the law have found, those tax cuts will gradually fade — and then morph into tax hikes for a majority of people who are solidly middle class.

Why?

Two features in the law — a child tax credit and a $10,000 limit on state and local tax deductions — won’t adjust to keep pace with inflation, thereby reducing their value each year. What’s more, the individual tax cuts are set to expire after 2025. And once the individual tax rates revert to their former levels, a stingier inflation gauge would raise taxes for most households.

President Donald Trump has largely sidestepped these trade-offs in promoting the overhaul he signed on Friday, a measure whose benefits largely favor corporations and wealthy individuals.

“It’s going to be a tremendous thing for the American people,” Trump said before signing the measure into law. “And I consider this very much a bill for the middle class and a bill for jobs.”

Trump has also said that “whoever” is president in 2025 would ensure that the expiring tax cuts for individuals are renewed. But doing so would cost heavily: The national debt would likely balloon by over $2 trillion — far more than the $1.5 trillion increase that lawmakers approved for the tax cuts — according to an analysis by the Committee for a Responsible Federal Budget.

The rising debt could eventually force spending cuts to social and educational programs that serve many who aspire to join the middle class. Trump and House Speaker Paul Ryan have both raised the prospect of reducing spending on social services next year, with Ryan specifically mentioning changes to Medicare.

Trump, Republican lawmakers and their allies are betting that higher take-home pay from the tax cuts will shore up public support for a law polls show a sizable number of Americans view unfavorably.

More than 80 percent of taxpayers will receive a tax cut in 2018, according to an analysis by the nonpartisan Tax Policy Center. These tax cuts skew most heavily toward the top 5 percent of earners. This group — with incomes starting at $307,900 — would collect 42.6 percent of the tax cuts. By 2027, they would enjoy no less than 99.2 percent of the tax cuts.

By contrast, a majority of people earning less than $93,200 would, on average, absorb a tax increase in 2027.