WASHINGTON — After a day of partisan bickering over whether the Republicans’ sweeping tax plan would truly help the middle class, a key House panel on Monday approved late changes. Lawmakers restored the tax exemption for employees receiving child-care benefits from their companies, but also put new requirements on a tax credit used by working people of modest means.

The House Ways and Means Committee voted 24-16 along party lines to adopt the amendment from its chairman, Rep. Kevin Brady, R-Texas. The changes were made to the complex Republican tax legislation put forward last Thursday.

The vote on the amendment capped a rancorous marathon session in which Republicans and Democrats argued heatedly over the nearly $6 trillion plan. Democrats repeatedly lodged objections to the bill, especially to its limits on prized deductions for homeowners and its repeal of the child adoption credit and the deduction for medical expenses.

It was the first of what are expected to be several days of work on the bill, as Republicans drive to push legislation through Congress and to President Trump’s desk by Christmas.

Republicans focused on findings by Congress’ nonpartisan Joint Committee on Taxation that the bill would lower taxes across all income levels over the next several years.

“Clearly this is helping real people. It’s helping teachers, it’s helping students, it’s helping struggling families that are living paycheck to paycheck,” said Republican Rep. Erik Paulsen of Minnesota.

Democrats returned repeatedly to a section of the analysis showing taxes would actually go up beginning in 2023 for some 38 million taxpayers or families making $20,000 to $40,000 a year.

“There are a lot of people expecting a tax cut who would be big losers under this bill,” proclaimed Democratic Rep. Bill Pascrell of New Jersey. “This is a joke and you’ve got to face up to it.”

At stake is whether Republicans will succeed in passing the most sweeping rewrite of the tax code in decades, after a year largely devoid of legislative wins. Looking ahead to 2018 midterms, Democrats and Republicans are both trying to win the debate over who is truly looking out for middle-class Americans.