AUSTIN — Republican Attorney General Ken Paxton is leading the fight to undo the nearly 10-year-old Affordable Care Act, with legal arguments scheduled Tuesday in New Orleans.

A win would thrust Paxton into the national spotlight, showcasing his conservative credentials on a major stage. But it could also create a political liability for Republicans ahead of the 2020 election when health care is poised to be a top issue.

More than 20 million Americans are potentially at risk of losing insurance coverage if the law is overturned — including over 900,000 people in Texas who buy insurance through the marketplace with federal subsidies, according to the Kaiser Family Foundation.

Even if the 5th U.S. Circuit Court of Appeals in New Orleans rules in Paxton’s favor, the case is expected to go before the U.S. Supreme Court, perhaps months before voting starts in November 2020.

Democrats say if Paxton wins, it would send the Texas GOP into a tailspin.

“This will be an issue to flip the Texas House, this will be an issue to expand the U.S. House majority, this will be an issue to take out (Republican U.S. Sen.) John Cornyn and this will be an issue to win Texas for the presidency," said Manny Garcia, executive director of the Texas Democratic Party.

Republican strategists say the fear is overblown, that no one would immediately lose insurance coverage if the law is stricken down and Obamacare has done nothing to lower health care costs.

“We’re fear-mongering on this pre-existing condition issue,” said Rob Henneke, general counsel with the Texas Public Policy Foundation, who is representing two individuals in the lawsuit. “But the reason why persons without insurance has been increasing is because the costs have been driving people out of the market because the restrictions of the ACA limit the choice and mandate the type of product you want to purchase.”

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Still, a number of the law’s provisions are popular with voters of all political stripes, including the protections for people with pre-existing conditions and rules allowing young adults to stay on their parents’ health insurance plans through age 26.

“The biggest risk is it provides Democrats with a wonderful campaign issue for 2020 across the country," said Mark Jones, a Rice University political scientist. “They can say ‘the Republicans have killed the ACA, so anyone who obtains benefits from it can find themselves in a worse position.’"

In the 2018 election, Democrats weaponized Republicans’ opposition, warning voters that a dismantling of the landmark healthcare law would unravel those pre-existing protections.

Republicans fought back, pledging to keep those protections, but little has happened to date. After Democrats seized control of the U.S. House last year, members of both parties are skeptical of any major health care compromise ahead of the 2020 race.

Paxton’s office didn’t return a request for comment.

He and previous Republican attorneys general in Texas have waged a long-running campaign to dismantle federal laws and policies that they call unconstitutional overreaches.

That mission statement is described clearly by the Republican Attorneys General Association, which Paxton heads as chairman, on its website: “to defend federalism, adhere to the law, and apply a common sense, free market approach to governing.”

Paxton told the Austin American-Statesman last week that the case will allow decisions about health care systems to return to state, rather than federal, hands.

“Obamacare is a failed social experiment,” Paxton told the Statesman. “The sooner it is invalidated, the better, so each state can decide what type of health care system it wants and how best to provide for those with pre-existing conditions, which is federalism that the Founders intended.”

The ACA case, as well as another over the legality of the Obama-era Deferred Action for Childhood Arrivals program that is expected to be heard in Texas federal district court in October, are among the most high-profile cases Paxton’s office will argue this year and possibly to date.

The ACA lawsuit shows Paxton is a leader who can pull together a group of states from across the country, said Corbin Casteel a lobbyist and Republican political strategist.

“He needs to win. We all needed to win,” he said. “There’s a better plan that’s more affordable for the American people.”

Republicans in Congress have long pledged to repeal and replace the Affordable Care Act, but they took their biggest step in 2017 by ending the financial penalty for not carrying health insurance — a key provision of the law referred to as the “individual mandate.”

That shift paved the way for Paxton’s lawsuit, which argues without the individual mandate, the entire health care law is unconstitutional.

The legal team derives its support from the 2012 Supreme Court ruling that the ACA was legal under Congress’ taxing powers. Since it no longer levies a tax, the lawyers argue, it lacks a legal foundation.

A federal district court judge in Texas ruled in Paxton’s favor in late 2018, a decision that a Democratic coalition of states quickly appealed.

The federal government, after President Trump was elected, changed its position and switched sides to join Paxton’s team. In its absence, a group of 20 Democratic attorneys general, led by California Attorney General Xavier Becerra, and the Democratic-controlled House of Representatives intervened in the case to defend the law.

The Democratic coalition will argue that the tax bill did not eliminate the penalty but rather reduced it to $0. At this time, it may act as more of a recommendation, they assert, but in the future, Congress could raise the amount and it would once again generate tax revenue.

Even if that part is ruled unconstitutional, however, they say the rest of the legislation can legally remain without it.

“Together, the Trump Administration and the Texas-led coalition risk the health of nearly every American — from the young to the elderly, the sick to the gainfully employed,” Becerra said.

“A bipartisan chorus of economists, scholars and medical groups agrees: this lawsuit blessed by President Trump has little regard for Americans' health, lives or the law. Our coalition of states stands ready to defend the law and every person whose life may be on the line."

Henneke, general counsel with the Texas Public Policy Foundation, said the law will likely not immediately disappear in the case of a victory, and states will have time to formulate their back-up plans. He encourages more states to follow Texas and Louisiana in preparing fallback plans now.

Gary Claxton, vice president of the Kaiser Family Foundation, said it’s not clear if the law is ruled unconstitutional by the U.S. Supreme Court whether the federal funding that pays for expanded Medicaid or insurance subsidies would abruptly end.

“I'm not sure anyone has thought through what it means to turn this off overnight,” he said. “It is hard to put the insurance markets back the way they were.”

Oral arguments begin at 1 p.m. Tuesday in the New Orleans courtroom.