WASHINGTON — President Donald Trump and congressional Republicans, despite repeated pledges to preserve sick Americans’ access to health coverage, are poised to scrap this core insurance protection in their campaign to roll back the Affordable Care Act.

Both the House GOP bill that passed in May and the revised Senate GOP bill unveiled last week effectively eliminate the coverage guarantee by allowing health insurers to sell skimpier plans and charge more to people with preexisting health conditions.

At the same time, the House and Senate bills dramatically scale back financial aid to low- and moderate-income consumers, and slash funding for Medicaid.

That combination — looser insurance requirements and less financial assistance for patients — will put health plans out of reach for millions of sick Americans, according to numerous analyses.

“The fundamental guarantee at the heart of the Affordable Care Act was that people who are sick can get insurance at the same price as everyone else,” said Larry Levitt, an insurance market expert at the nonprofit Kaiser Family Foundation. “The House and Senate replacement bills move the system back to a place where healthy and sick people are treated very differently.”

The Senate was slated to begin voting on its health care bill this week, but Sen. John McCain announced Saturday he would be staying in Arizona at least a a week following surgery for a blood clot above his left eye. That put the measure in jeopardy in the closely divided Senate, and Senate Majority Leader Mitch McConnell said he would defer consideration of the legislation.

ACA’s coverage guarantee remains among the most popular parts of the 2010 law, with nearly seven in 10 Americans rating it favorably. Trump administration and GOP congressional officials insist the Republican bills won’t leave anyone behind.

“The legislation ensures that every American with preexisting conditions has access to the coverage and care they need, no exceptions,” Vice President Mike Pence told a meeting of the National Governors Association on Friday.

But that assurance has been contradicted by nearly every independent evaluation of the health care bills, including two reports by the nonpartisan Congressional Budget Office. Pence’s claims are also at odds with the assessment of health insurers.

On Friday, the heads of the industry’s two leading advocacy groups — America’s Health Insurance Plans and the Blue Cross Blue Shield Association — called the Senate bill “simply unworkable,” warning it “would undermine protections for those with preexisting medical conditions.”

Similarly, in a letter to Senate leaders this month, the American Academy of Actuaries warned that provisions of the Senate bill “could erode preexisting condition protections” and “make it more difficult for high-cost individuals and groups to obtain coverage.”

Nearly every major patient advocacy organization has reached the same conclusion.

“Older and sicker individuals … would face the full cost of these higher premiums, leaving millions of people with chronic conditions and disabilities unable to afford the kind of coverage they need,” a coalition of 13 patient groups wrote to senators last week, condemning the Senate bill.

The coalition includes the American Heart Association, the American Lung Association and the advocacy arm of the American Cancer Society.

The kind of deregulated insurance markets envisioned by the House and Senate bills would mark a return to what health insurance looked like before the current health care law was enacted.

Before Obamacare, as the ACA is known, most insurance companies worked aggressively to exclude sick customers, either denying coverage or charging unaffordable prices to people with preexisting conditions. That left millions of Americans with next to no option for coverage.

Although some states offered special health plans for sick patients who’d been rejected by insurers, most of these limited benefits or capped enrollment because coverage was costly.

“It was a medical gulag,” said Richard Figueroa, former enrollment director of California’s plan, which had long waiting lists because demand always outstripped money available.

Obamacare equalized how health insurance treats patients. Insurers were not only forbidden to deny coverage to sick consumers, they had to provide a basic set of benefits. That standardization ensured that the sick were not forced to pay more for insurance than the healthy.

This meant higher costs for some consumers. But uniform standards are necessary to ensure equal access to coverage, said Manatt Health Managing Director Joel Ario, a former insurance commissioner in Oregon and Pennsylvania.

Republicans have stressed that their legislation does not repeal the coverage guarantee that prohibits insurers from denying coverage. Last week, Senate GOP leaders said they want to give consumers the opportunity to find more affordable coverage.

“We think it’s great to give people more options and more choices and the freedom to actually buy the insurance products they want,” said Sen. John Thune, R-S.D.

noam.levey@latimes.com