Washington — Democrats drove their election-year economic package toward Senate approval on Sunday, debating a measure with less ambition than President Biden’s original domestic vision but that touches deep-rooted party dreams of slowing global warming, moderating pharmaceutical costs and taxing immense corporations.

Debate began Saturday and by sunrise on Sunday, Democrats had swatted down a dozen Republican efforts to torpedo the legislation, with no clear end in sight. Despite unanimous GOP opposition, Democratic unity in the 50-50 chamber — buttressed by Vice President Kamala Harris’ tiebreaking vote — suggested the party was on track for a morale-boosting victory three months from elections when congressional control is at stake.

The House planned to return briefly from summer recess Friday for what Democrats hope will be final congressional approval.

“I think it’s gonna pass,” Mr. Biden told reporters as he left the White House early Sunday to go to Rehoboth Beach, Delaware, ending his COVID-19 isolation. The House seemed on track to provide final congressional approval when it returns briefly from summer recess on Friday.

“It will reduce inflation. It will lower prescription drug costs. It will fight climate change. It will close tax loopholes and it will reduce and reduce the deficit,” Senate Majority Leader Chuck Schumer, a Democrat of New York, said of the package. “It will help every citizen in this country and make America a much better place.”

Republicans said the measure would undermine an economy that policymakers are struggling to keep from plummeting into recession. They said the bill’s business taxes would hurt job creation and force prices skyward, making it harder for people to cope with the nation’s worst inflation since the 1980s.

“Democrats have already robbed American families once through inflation, and now their solution is to rob American families a second time,” Senate Minority Leader Mitch McConnell of Kentucky argued. He said spending and tax increases in the legislation would eliminate jobs while having insignificant impact on inflation and climate change.

Sen. Rick Scott, a Republican from Florida, too, said the plan will raise taxes and harm the economy.

“We shouldn’t be cutting Medicare like this,” Scott said in an interview on “Face the Nation.” “We shouldn’t be raising taxes ever but especially in a recession. And why would we be raising the taxes on gas right now when it’s $2 above what it was when Joe Biden took office. This is going to continue to drive us into a bigger recession than we are.”

Nonpartisan analysts have said Democrats’ “Inflation Reduction Act” would have a minor effect on surging consumer prices. The bill is barely more than one-tenth the size of Biden’s initial 10-year, $3.5 trillion rainbow of progressive aspirations and abandons its proposals for universal preschool, paid family leave and expanded child care aid.

Even so, the new measure gives Democrats a campaign-season showcase for action on coveted goals. It includes the largest ever federal effort on climate change — close to $400 billion — hands Medicare the power to negotiate pharmaceutical prices and extends expiring subsidies that help 13 million people afford health insurance.

But Scott predicted the plan will be a boon for GOP candidates on the ballot in November.

“This bill is not going to help Democrats. It’s going to help Republicans,” he told “Face the Nation.” “Raising taxes $700 billion, cutting Medicare $280 billion, raising gas taxes, having 87,000 more IRS agents. Do you know how happy people are to have more IRS agents out there? I mean, this is not going to be popular around the country.”

Mr. Biden’s original measure collapsed after conservative Democratic Sen. Joe Manchin of West Virginia opposed it, saying it was too costly and would fuel inflation.

In an ordeal imposed on all budget bills like this one, the Senate descended into an hourslong “vote-a-rama” of rapid-fire amendments. Each tested Democrats’ ability to hold together a compromise negotiated by Schumer, progressives, Manchin and the inscrutable centrist Democratic Sen. Kyrsten Sinema of Arizona.

Progressive Sen. Bernie Sanders of Vermont offered amendments to further expand the legislation’s health benefits, and those efforts were defeated. But most proposed changes were fashioned by Republicans to unravel the bill or force Democrats into votes on dangerous political terrain.

One GOP proposal would have forced the Biden administration to continue Trump-era restrictions that cited the pandemic for reducing the flow of migrants across the Southwest border.

Earlier this year, Democrats facing tough reelections supported such an extension, forcing the party to drop its push for COVID-19 spending when Republicans conjoined the two issues. This time, with their far larger economic legislation at stake and elections approaching, Democrats rallied against the border controls.

Other GOP amendments would have required more gas and oil leasing on federal lands and blocked a renewal of a fee on oil that helps finance toxic waste cleanups. All were rejected on party-line votes. Republicans accused Democrats of being soft on border security and opening the door to higher energy and gas costs.

Before debate began Saturday, the bill’s prescription drug price curbs were diluted by the Senate’s nonpartisan parliamentarian. Elizabeth MacDonough, who referees questions about the chamber’s procedures, said a provision should fall that would impose costly penalties on drug makers whose price increases for private insurers exceed inflation.

It was the bill’s chief protection for the 180 million people with private health coverage they get through work or purchase themselves. Under special procedures that will let Democrats pass their bill by simple majority without the usual 60-vote margin, its provisions must be focused more on dollar-and-cents budget numbers than policy changes.

But the thrust of their pharmaceutical price language remained. That included letting Medicare negotiate what it pays for drugs for its 64 million elderly recipients, penalizing manufacturers for exceeding inflation for pharmaceuticals sold to Medicare and limiting beneficiaries out-of-pocket drug costs to $2,000 annually.

Democrats wanted to include a provision in the bill that would have capped patients’ costs for insulin, the expensive diabetes medication, at $35 monthly. But that proposal ran afoul of the parliamentarian’s ruling that it couldn’t be added, and Democrats failed to garner the 60 votes needed to disregard the rule, by a vote of 57 to 43 on Sunday morning.

The measure’s final costs were being recalculated to reflect late changes, but overall it would raise more than $700 billion over a decade. The money would come from a 15% minimum tax on a handful of corporations with yearly profits above $1 billion, a 1% tax on companies that repurchase their own stock, bolstered IRS tax collections and government savings from lower drug costs.

Sinema forced Democrats to drop a plan to prevent wealthy hedge fund managers from paying less than individual income tax rates for their earnings. She also joined with other Western senators to win $4 billion to combat the region’s drought.

It was on the energy and environment side that compromise was most evident between progressives and Manchin, a champion of fossil fuels and his state’s coal industry.

Clean energy would be fostered with tax credits for buying electric vehicles and manufacturing solar panels and wind turbines. There would be home energy rebates, funds for constructing factories building clean energy technology and money to promote climate-friendly farm practices and reduce pollution in minority communities.

Manchin won billions to help power plants lower carbon emissions plus language requiring more government auctions for oil drilling on federal land and waters. Party leaders also promised to push separate legislation this fall to accelerate permits for energy projects, which Manchin wants to include a nearly completed natural gas pipeline in his state.