A lawsuit filed by20 Republican states calls on federal courts to find the healthlaw's protections for people with pre-existing conditionsunconstitutional. (Photo: Shutterstock)

If the Affordable Care Act's protections for people withpreexisting medical conditions are struck downin court, residents of the Republican-led states that are challenging the law have the most to lose.

“These states have been opposed to the ACA from the beginning,”said Gerald Kominski, a senior fellow at the UCLA Center for HealthPolicy Research. “They're hurting their most vulnerable citizens.”

Related: Majority of GOP voters support pre-existingcondition coverage

Twenty Republican state attorneys general and governors challenged the constitutionality of the ACA in federal court inFebruary. Last month, U.S. Attorney General Jeff Sessions and theDepartment of Justice made the unusual decision not to defend keyportions of the law against this legal challenge.

The states' lawsuit argues that because Congress eliminated theObamacare tax penalty for not having insurance coverage, effectivenext year, the entire law is unconstitutional. By extension, thesuit calls on federal courts to find the health law's protectionsfor people with preexisting conditions unconstitutional — andSessions agrees.

Nine of the 11 states with the highest rates of preexistingconditions among adults under 65 have signed onto the lawsuit tostrike down the ACA, according to data from insurance companies andthe U.S. Centers for Disease Control and Prevention. The 2015 data, the most recent available, were analyzed by theKaiser Family Foundation in 2016. (Kaiser Health News, whichproduces California Healthline, is an editorially independentprogram of the foundation.)

Those who support the lawsuit contend that there are other meansof protecting people with preexisting conditions.

“If a court strikes down the constitutionality of the ACA, thereare ways to repeal and replace without Arizonans with preexistingconditions losing their coverage,” said Katie Conner, a spokeswomanfor Arizona Attorney General Mark Brnovich.

Conner said her boss, who is party to the lawsuit, believespreexisting conditions should “always be covered.” In Arizona, morethan 1 in 4 adult adults under 65 have a preexisting condition,according to the data.

The state with the highest rate of adults with preexistingconditions is West Virginia — 36 percent of those under age 65.That means that about 1 in 3 of them could have a hard time buyinginsurance through the individual marketplace without the ACAprotections.

The office of West Virginia Attorney General Patrick Morrisey,who joined the legal challenge against the ACA, declined tocomment. But a spokesman for Morrisey's re-election campaign told PolitiFact last month that “help should beprovided to those who need it most, including those withpreexisting conditions.”

Plaintiffs in the lawsuit “are paying lip service to thesecritical protections for people, but they are in fact engaged in astrategy that would get rid of those protections,” said JustinGiovannelli, an associate research professor at GeorgetownUniversity's Center on Health Insurance Reforms. “Frankly, it'shard to square what they're saying on the one hand and what they'rearguing in the courts on the other.”

According to a poll released in June, also by the Kaiser Family Foundation,three-quarters of Americans say that maintaining protections forpeople with preexisting conditions is “very important.” Thisincludes majorities of Democratic, Republican and independentvoters.

Before the health law was adopted, insurance companies routinelydenied coverage to millions of people with preexisting conditions who purchasedinsurance through the individual marketplace. If they didn't denycoverage outright, some health plans charged consumers exorbitantpremiums, or offered policies that excluded coverage for priceyconditions. (Although many people got insurance through theiremployers or public plans that covered preexisting conditions, theycould have been left vulnerable if their employment status or othercircumstances changed.)

The ACA ended those practices.

Common conditions that led insurance companies to deny coverageincluded high blood pressure, cancer, obesity, diabetes anddepression, among many others. Some people were denied for havingacne, asthma or for being pregnant.

The KFF analysis estimated that at least 27 percent of adultsunder 65 — more than 50 million Americans — had at least onepreexisting condition that would have jeopardized their coveragepre-ACA. The foundation said its estimates were an undercountbecause some diseases that insurers cited when declining coverageare not in the survey data. Also, each insurance company set itsown rules and conditions for denials, making accurate counts ofthose who could be affected hard to nail down.

Less precise estimates by other researchers and the Departmentof Health and Human Services show that up to half of all adults under age 65 have at least onepreexisting condition.

This story was produced by KaiserHealth News, which publishes California Healthline, aservice of the California HealthCare Foundation.

Kaiser HealthNews (KHN) is a national health policy news service. It is aneditorially independent program of the Henry J. Kaiser Family Foundation whichis not affiliated with Kaiser Permanente.