The states' lawsuit argues that because Congress eliminated the Obamacare tax penalty for not having insurance coverage, effective next year, the entire law is unconstitutional. By extension, the suit calls on federal courts to find the health law's protections for people with preexisting conditions unconstitutional — and Sessions agrees.

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

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

“If a court strikes down the constitutionality of the ACA, there are ways to repeal and replace without Arizonans with preexisting conditions losing their coverage,” said Katie Conner, a spokeswoman for Arizona Attorney General Mark Brnovich.

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

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

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

Plaintiffs in the lawsuit “are paying lip service to these critical protections for people, but they are in fact engaged in a strategy that would get rid of those protections,” said Justin Giovannelli, an associate research professor at Georgetown University's Center on Health Insurance Reforms. “Frankly, it's hard to square what they're saying on the one hand and what they're arguing 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 for people with preexisting conditions is “very important.” This includes majorities of Democratic, Republican and independent voters.

Before the health law was adopted, insurance companies routinely denied coverage to millions of people with preexisting conditions who purchased insurance through the individual marketplace. If they didn't deny coverage outright, some health plans charged consumers exorbitant premiums, or offered policies that excluded coverage for pricey conditions. (Although many people got insurance through their employers or public plans that covered preexisting conditions, they could have been left vulnerable if their employment status or other circumstances changed.)

The ACA ended those practices.

Common conditions that led insurance companies to deny coverage included high blood pressure, cancer, obesity, diabetes and depression, among many others. Some people were denied for having acne, asthma or for being pregnant.

The KFF analysis estimated that at least 27 percent of adults under 65 — more than 50 million Americans — had at least one preexisting condition that would have jeopardized their coverage pre-ACA. The foundation said its estimates were an undercount because some diseases that insurers cited when declining coverage are not in the survey data. Also, each insurance company set its own rules and conditions for denials, making accurate counts of those who could be affected hard to nail down.

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

This story was produced by Kaiser Health News, which publishes California Healthline, a service of the California Health Care Foundation.

Kaiser Health News (KHN) is a national health policy news service. It is an editorially independent program of the Henry J. Kaiser Family Foundation which is not affiliated with Kaiser Permanente.