Adding to that vulnerability is the law’s relatively low popularity. After a brief high shortly after enactment, the tax-cut measure has failed to attract the support of a majority of Americans in polling.

Many Democrats won House seats after promising to repeal all or part of the tax law — particularly the SALT limit, which appears to have hurt Republican candidates in high-income, high-tax districts in areas like Orange County, Calif., and the New Jersey suburbs of New York City. But since the election, those promises have been overtaken by a flurry of legislative and campaign proposals to raise taxes on the rich.

Representative Alexandria Ocasio-Cortez of New York has proposed raising the top marginal income tax rate to 70 percent for people with incomes above $10 million. Senator Elizabeth Warren of Massachusetts, a presidential candidate, recently unveiled a plan to levy a 2 percent annual wealth tax on Americans with a net worth exceeding $50 million. And Senator Kamala Harris of California, who is also running for president, says her top policy priority is a tax cut for low- and middle-income Americans that could cost nearly $3 trillion over a decade.

You don’t need to spend a minute wondering if those plans might pass Congress this year: They won’t.

Only a few tax changes are even remotely likely to affect you this year. Congress could decide to extend some expired tax credits retroactively, such as deductions for private mortgage insurance and higher-education expenses, Ms. Kaeding said. Such a move would simply continue tax credits that some taxpayers had come to depend on, which otherwise would vanish for the 2018 tax year and beyond.

There’s a small chance that Democrats and Republicans might work together to slightly tweak tax advantages for retirement savings, but analysts see that as a long shot, at best.

The Trump administration is also considering pleas from some conservative groups to allow taxpayers to reduce their capital gains taxes by adjusting the initial value of an asset, such as a home or a share of stock, for inflation when it sells. The groups say that change would accelerate economic growth by freeing more money for investment. Previous administrations have concluded that such a move is outside the power of the executive branch, but many groups pushing for lower taxes have been meeting regularly with administration officials, urging them to make the change.