WASHINGTON — Six bills that could reshape the power of the tech industry passed an important hurdle in the House. But the outcomes of the votes, and the debates before they took place, also showed divisions among lawmakers — and underscored why final passage of the package is expected to be difficult.

In a marathon session of debate and voting that started Wednesday morning and continued into Thursday, the Judiciary Committee advanced the suite of bills, which are meant to weaken the dominance of Big Tech. The bills would bulk up antitrust agencies, make it harder to acquire potential rivals and prevent platforms from selling or promoting their own products to disadvantage competitors.

Democrats, who have had the most say over the bills and who overwhelmingly support the proposals, are focused on the market power of Amazon, Apple, Facebook and Google. Representative Jerrold Nadler of New York, the Democratic chairman of the committee, said the votes “pave the way for a stronger economy and a stronger democracy for the American people by reining in anticompetitive abuses of the most dominant firms.”

A handful of Republicans joined Democrats in approving the proposals. Those Republicans argue that the proposals would help address one of their main concerns: the power that social media companies have over speech, and what they argue is political bias and censorship of conservative voices.

But many other Republicans say that the bills only add more government intervention while not directly addressing their concerns about free speech.

That debate within the Republican Party spilled out on Wednesday as soon as the first bill was brought up for a vote. The proposal, considered among the least contentious of the six, would increase the costs of fees associated with some mergers to help raise more funding for the Federal Trade Commission and the Department of Justice, which regulate deals.

During a three-hour debate about the bill, Representative Jim Jordan of Ohio, the top Republican on the committee, said it was a power grab for the Democrat-led antitrust agencies, making them bigger and more influential. He also said the antitrust bills failed to address the ability of Facebook and other social media companies to cut off political voices.

“Big tech censors conservatives,” Mr. Jordan said. “These bills don’t fix that problem; they make it worse.”

Representative Ken Buck of Colorado, a fellow Republican and a co-sponsor of the bills, agreed that the tech companies silence conservatives. But he implored his party for unity to take on the power of Big Tech, saying the proposals would limit the overall power of the companies.

“These bills are conservative,” Mr. Buck said.

While progressive lawmakers largely back the bills, the proposals have frustrated Democratic lawmakers from California, who say they go too far in regulating their state’s most prominent companies.

Representative Lou Correa, a Democrat from Southern California, said that the number of people in the state working for the big tech companies had grown substantially, helping to fund services like public education and support for people affected by Covid.

“These firms — high tech — are the reason California has a budget surplus, as opposed to a deficit,” he said, adding later: “We want to make sure that we don’t kill the goose that lays the golden eggs.”

Other California Democrats who expressed concerns about the bills included Representative Zoe Lofgren, whose district includes part of San Jose, and Representative Eric Swalwell.

Ms. Lofgren worried during the hearing that the bills could ensnare companies that do not share the tech giants’ immense scale. Mr. Swalwell said before the hearing even began that he would oppose several of the bills.

“In my district alone, I represent thousands — likely in the five digits — of employees affected by the proposed laws,” he said. “It is these people whose jobs, families and livelihoods I was elected to protect — and must advocate for today.”

The committee’s passage of the bills kicks off a much harder process. Eight Democratic lawmakers have asked Speaker Nancy Pelosi, who has tremendous sway over when bills are taken up in the full House, to slow the process. The lawmakers repeated arguments made by companies like Apple that the bills could open up security and privacy vulnerabilities for customers.

Ms. Pelosi said at a Thursday news conference that she had told concerned tech companies to substantively participate in the process of crafting the legislation as it moved through the House, but she noted that lawmakers from both parties had grown concerned about Silicon Valley’s power.

“They can put forth what they want to put forth,” she said. “But we’re not going to ignore the consolidation that has happened and the concern that exists on both sides of the aisle.”

The challenge is even stiffer in the Senate, where the bills will each require significant Republican support to reach the 60 votes needed to override the legislative filibuster. A few Republicans, including Josh Hawley of Missouri, have pressed for stiffer antitrust laws. But it is unclear whether many more will join him.

Some bills, like the one to generate more money for regulators, could face less resistance than others. The committee approved that bill on Wednesday by a vote of 29 to 12. The sixth and final bill, a measure that could break apart elements of the tech giants’ businesses, was approved on Thursday afternoon 21 to 20.

“We think it’s an uphill climb for the toughest bills,” said Paul Gallant, a research analyst at Cowen and Company. “The Senate filibuster is always the highest hurdle, and I suspect it will hold back the toughest of these bills. But the House is going faster and farther against tech than anyone expected.”

The bills face fierce opposition from technology companies, which have marshaled their considerable lobbying operations. Ahead of the votes on Wednesday, Apple sent a letter to committee leaders warning that if the bills were passed, it would not be able to offer certain privacy and security features for users. Think tanks and lobbying groups funded by tech companies issued critical statements before the votes.

The bills “single out a handful of America’s most innovative and globally competitive tech companies for divestiture and draconian regulation,” said Alec Stapp, a director of the Progressive Policy Institute, a nonprofit think tank that received sponsorship from tech companies.

Chamber of Progress, a newly formed trade group representing Amazon and Google, said that a recent Morning Consult survey showed that voters didn’t see tech regulation as a top priority.

“Consumers want the government to scrutinize and regulate the tech industry, but don’t want Congress redesigning the apps and services that make their lives easier,” said the Chamber of Progress’s chief executive, Adam Kovacevich.

Alex Harman, a competition policy advocate at Public Citizen, which has been pushing for the bills, said Wednesday’s votes represented an important moment. Almost a decade ago, he said, there had been little Capitol Hill support for an investigation of Google’s practices by the Federal Trade Commission, which ultimately decided not to pursue a case against the company.

“Nine years later, we are in a world where a serious bipartisan effort in a committee is not just trying to push on an investigation, they’re trying to break them up,” he said. “That is a big deal.”