"Democrats are going to do what it takes to expand the child tax credit," House Minority Leader Nancy Pelosi, D-Calif., said. "How do we say to the children of those families, 'Your parents work, but they don't make enough money to get this tax credit?'"
Republican leaders in the House said they may consider the idea, but some officials tell the New York Times that the House GOP may only expand the child tax credit as part of a larger package of additional tax cuts totaling $100 billion or more.
A figure that large would lose support from deficit-hawkish Senators, creating a potential roadblock.
House GOP leaders also bristled at claims that President Bush's tax cuts have left poor workers behind.
"This notion that we are not taking care of the poor working families of this country is completely false," said Rep. Tom DeLay, R-Texas.
Conservatives argued strongly that those workers already get their income taxes and much of their payroll taxes refunded through the earned income tax credit. That program is designed to lift workers out of poverty and encourage them to stay off welfare.
"Do we want the government to write bigger checks?" said Republican Sen. Don Nickles of Oklahoma, one of two senators to oppose the tax package when the Senate voted 94-2 on Thursday to pass the bill. His Oklahoma colleague James Inhofe, also a Republican, was the other "no" vote.
The Senate faced strong political pressure to expand the benefit and Democrat Blanche Lincoln of Arkansas amassed a majority of the Senate behind the idea.
"These are hardworking couples who put in a hard day's work," said Lincoln. "They're trying desperately to raise a family."
The tax cut enacted last month increased the child tax credit from $600 to $1,000 and instructed the Treasury Department to send advance refunds worth $400 per child to families who qualify for the expanded benefit.
About 25 million middle-income families would receive checks. But the law did not change the eligibility rules for low-income families. The Center on Budget and Policy Priorities calculated that lawmakers had left out families that make between $10,500 and about $27,000.
The bill passed Thursday by the Senate would allow low-income families to claim a child tax credit worth 15 percent of their income over $10,500. A full-time worker earning minimum wage makes $10,300 a year.
Some would get an advance refund with other families later this summer if Congress sends the bill to the president by June 23. Those who don't earn enough to take the full $1,000 credit would have to claim the refund when they file their taxes next year.
Republicans matched the benefit for low-income workers with a bigger child credit for wealthier married couples. In 2008 and 2009, married couples who make up to $115,000 can claim the full benefit. In 2010, couples who make up to $150,000 can claim the entire credit. The child tax credit starts to phase down for couples who earn $110,000 or more under current law.
The bill also reduces the five definitions of a "child" used for various tax deductions and credits to a single definition. Its $10 billion cost is paid for by extending customs fees.
The House could pass the bill or negotiate with the Senate in a conference. The House's Republican leadership did not immediately embrace either approach.
"You never say never," said DeLay, who has vowed to bring two or three more tax bills up for debate this year.
The Senate's move to expand the child tax credit does not resolve another quirk in the bill that denies tax reductions to 8.1 million taxpayers who are single without children and in the lowest tax bracket, or who file as a "head of household," according to the Center for Budget and Policy Priorities.