The proposal retains many of the popular consumer protections of the Affordable Care Act, including ensuring that people with pre-existing medical conditions cannot be refused coverage or charged more.
MacArthur, on his Facebook page, said the plan "will make coverage of pre-existing conditions sacrosanct for all Americans."
But the plan also allows states to waive those protections.
If states requested waivers, people with pre-existing conditions would likely be covered through state-run high-risk pools, which can be expensive for patients and for taxpayers. Many states used high-risk pools before Obamacare with limited success because they weren't adequately funded, according to a study by the Kaiser Family Foundation.
The plan "would make coverage unaffordable for many older consumers and would segregate high cost consumers in coverage that would likely be inadequate," says Timothy Jost, an emeritus professor at Washington and Lee Law School who writes a health policy blog for Health Affairs.
The proposal could also cause premiums to spike for people with medical issues, according comments posted on Twitter by Topher Spiro, vice president for health policy at the left-leaning Center for American Progress. A person with diabetes could see premiums rise by about $5,600 while someone with metastatic breast cancer could be charged an additional $142,650, he says.
There are some protections against such premium spikes in the proposal, says Rodney Whitlock, vice president of health policy at ML Strategies who was a Republican Senate staffer when the Affordable Care Act was passed.
He says language that forces states to promise their changes would still protect people with pre-existing conditions, and result in lower premiums, invites people hurt by the changes to sue the state.
The proposal doesn't mention Medicaid at all, so it may do little to bring in support for the Republican bill. That's because the American Health Care Act was killed in part because it rolled back Medicaid coverage for millions of low-income people, something moderate Republicans opposed.
"I have a hard time believing that this will be acceptable to moderates in the House, much less the Senate, and will certainly be opposed by all Democrats," Jost says.