The prospect of millions of people unable to afford coverage led to an outcry from the health care industry as well as consumer groups. They found an uncommon ally in some insurers, who rely heavily on Medicaid and Medicare as mainstays of their business and hope the Senate will be more receptive to their concerns. Hospitals, doctors, health insurers and some consumer groups, with few exceptions, are speaking with one voice and urging significant changes to the Republican health care legislation that passed the House on Thursday.

In contrast to hospital and doctor groups, insurers had largely remained silent about their reservations, perhaps in the hopes of bartering their low profile in exchange for assurances that billions of dollars in subsidies for low-income coverage would continue, according to a report in today’s New York Times. The White House and Congress have gone back and forth about their willingness to pay for the subsidies, prompting anxiety among some companies. Several, including Anthem, have threatened to sharply raise their prices or leave markets altogether without the funding.

But a few, including Blue Shield of California, came out in opposition to the bill before the vote. “We feel compelled to oppose it,” said Paul Markovich, the company’s chief executive. “It raises the specter that the sickest and neediest among us will be disproportionately hit in losing access.” The overriding concern — for insurers, many workers and officials throughout the health care systems in many states — is the broad reductions proposed for Medicaid. Even for insurers that have largely abandoned the individual market, like UnitedHealth Group and Aetna, a substantial portion of their business is providing coverage under Medicaid. The same is true for many local nonprofit plans. Employers and others said they were also concerned about the effects on freelancers, who do not have a traditional employer but are self-employed or contract workers in the so-called gig economy.

The health legislation now goes to the U.S. Senate, which had indicated “gutting” the House’s bill before sending it to President Trump.

The recent amendments to the bill also raised questions about coverage for people with pre-existing medical conditions, which has become an emotional flash point for opposition. The bill would allow states to waive some of the current rules banning insurers from charging sick people more or excluding certain benefits, and those waivers could have broad effects if employers are no longer required to provide comprehensive coverage. Before the Affordable Care Act, many employers capped how much they would pay for care over a person’s lifetime at $2 million. While it is unclear what states would allow under a waiver or when such waivers would go into effect, employers could revisit the limits and drop types of benefits if a state deemed them nonessential.

Some health care groups, like medical device manufacturers, supported the bill because of specific provisions like the repeal of a 2.3 percent device tax under the Affordable Care Act. That tax was suspended for two years in 2015, but the industry wants a permanent repeal. The Pharmaceutical Research and Manufacturers of America, the drug industry’s largest trade group, said it had not taken a position on the bill.

Unlike doctors and hospitals, which would most likely experience an immediate hit if millions of Americans lost insurance, medical device manufacturers and the drug industry would probably feel a more muted effect. The drug industry, for example, might sell fewer products and lose revenue.