The final word on striking down law will almost certainly come from the Supreme Court, which has twice upheld the 2010 legislation.
Nevada Gov. Steve Sisolak, a Democrat, signed a bill earlier this year prohibiting health insurers from denying coverage to patients due to pre-existing conditions, a pre-emptive move in case the Affordable Care Act were struck down.
He said this week in Salt Lake City at the summer meeting of the National Governors Association that he would ask his recently created patient protection commission to come up with recommendations for how to ensure patients don't lose coverage if the law is overturned, which would impact about 200,000 people enrolled in Medicaid expansion in Nevada.
"To rip that away from them would be devastating to a lot of families," Sisolak said.
Nevada is among a coalition of 20 Democratic-leaning states led by California that appealed the lower court ruling and is urging the appeals court to keep the law intact.
At a news conference Thursday, Democrats touted the protections they've passed to prevent people from losing health coverage.
Newsom said the state is looking at Massachusetts' state-run health care program and investigating if a single-payer model would work as possible options if the law is spiked.
"The magnitude is jaw-dropping," Newsom said. "You can't sit back passively and react to it."
Arkansas Gov. Asa Hutchinson, a Republican, said states need Congress to be ready to quickly pass a new health care plan if the court overturns Obama's law, since doing so would cut off federal funding for Medicaid expansion.
A court decision in March blocked Arkansas from enforcing work requirements for its Medicaid expansion program, which has generated seemingly annual debate in that state's Legislature about whether to continue the program.
"Congress can't just leave that out there hanging," Hutchinson said.
The 2018 lawsuit that triggered the latest legal battle over the Affordable Care Act was filed by a coalition of 18 Republican-leaning states including Arkansas, Arizona and Utah.
Arizona Gov. Doug Ducey, a Republican, said he wants to see how the court rules before he makes any decisions about how his state would deal with the loss of Medicaid funds but that Arizona has backup funds available.
"They're going to rule how they're going to rule and we'll deal with the outcome," Ducey said. "The best plans are to have dollars available."
It is unknown when the three-judge panel will rule.
The government said in March that 11.4 million people signed up for health care via provisions of the Affordable Care Act during open enrollment season, a dip of about 300,000 from last year.
Utah Gov. Gary Herbert, a Republican, said if the law is overturned, it would provide a perfect opportunity for Congress to try to craft a better program with support from both political parties.
He said his state, which rolled out its partial Medicaid expansion in April, probably will not start working on a contingency plan for people who would lose coverage until the appeals court rules.
"It's been talked about for so long, people are saying 'Why worry about it until it happens?'" Herbert said. "I think there's a little bit more of a lackadaisical thought process going on."
President Donald Trump, who never produced a health insurance plan to replace Obama's health care plan, is now promising one after the elections.
Newsom warned Americans not to rely on that.
"God knows they have no capacity to deal with that," Newsom said. "The consequences would be profound and pronounced."