ap photo House Ways and Means Committee Chairman Richard Neal, D-Mass., presides over a markup hearing to craft the Democrats’ Build Back Better Act, massive legislation that is a cornerstone of President Joe Biden’s domestic agenda, at the Capitol in Washington, Thursday.

WASHINGTON — House Democrats began pushing plans for providing paid family and medical leave, easing climate change and bolstering education through House committees Thursday as they battled Republicans and among themselves over President Joe Biden’s $3.5 trillion vision for reshaping federal priorities.

Five committees worked on their slices of the 10-year proposal, early steps in what looms as a fraught autumn for Democrats hoping to enact a remarkable range of major policy changes. They face not only solid GOP opposition but internal divisions among progressives and moderates in a Congress they control so narrowly that they can afford only three House defections, none in the Senate.

“We have a once-in-a-generation chance to make transformative, beneficial change,” said House Ways and Means Committee Chairman Richard Neal, D-Mass., as his tax-writing panel debated its pivotal chunk of the voluminous legislation. “This is our moment to lay a new foundation of opportunity for the American people.”

Republicans cast the still-evolving measure as an economy killer that would raise taxes, cost jobs, worsen federal debt and make people increasingly reliant on government. In a signal of the broad political potency they believe the chaotic U.S. withdrawal from Afghanistan offers, they repeatedly conjured that image to belittle Democrats’ economic plans.

“Following the humiliating Afghanistan surrender, now President Biden is leading America on an economic surrender to China, Russia, Europe and the Middle East,” said the top Republican on Ways and Means, Rep. Kevin Brady of Texas.

At a sixth committee, Democrats controlling the House Energy and Commerce panel unveiled new details supporting Biden’s push to wean power plants off climate-damaging fossil fuels by 2035. That included $150 billion in grants for utilities investing in cleaner energy sources plus millions of dollars in penalties for companies that don’t boost clean electricity output by at least 4% annually.

They also released their blueprint for retooling Medicare, Medicaid, children’s health insurance and the 2010 health care law. There were few surprises, but the proposals, which face votes next week, underscored Democrats’ intent to reinforce the pillars of the nation’s health care system with new benefits, lower costs and expanded insurance coverage.

In an early manifestation of unrest, one Democrat on the Ways and Means panel voted against the first two sections of her party’s bill after complaining that lawmakers lacked information on its cost and hadn’t been shown key portions dealing with taxes and prescription drug prices.

Moderate Rep. Stephanie Murphy, D-Fla., is co-chair of the House Blue Dog Coalition, a centrist group whose members include some of Congress’ most conservative Democrats. On one of those votes, outgoing moderate Rep. Ron Kind, D-Wis., joined her in voting “no.”

“I don’t know how much we’re spending, how much we’re raising, how we’re spending some of the money and how we’re raising any of the money,” Murphy told her colleagues.

Democrats have said they will pay for much of the overall bill by raising taxes on the rich and corporations. They’ve said no one earning under $400,000 annually would face higher levies.