House Minority Leader Nancy Pelosi, (D-CA) gestures during a news conference held by House Democrats condemning the Trump Administration's targeting of the Affordable Care Act's pre-existing condition, in the US Capitol on June 13, 2018 in Washington, DC.

A majority of Democrats and Republicans want to preserve protections in the Affordable Care Act that make it illegal for insurers to deny coverage to people with pre-existing conditions, according to a new poll.

Opening arguments in a lawsuit challenging the constitutionality of the ACA are set to begin in federal court in Texas on Wednesday. Although the lawsuit was brought by 20 Republican state attorneys general, the Kaiser Family Foundation found that 75 percent of Americans don't want those protections reversed. Some 58 percent of Republicans and 86 percent of Democrats want the provision guarding pre-existing conditions to remain intact, according to the poll of more than 1,200 adults from Aug. 23 through Aug. 28.

"Four in 10 Americans (41%) say they are 'very worried' that they or a family member will lose coverage if the Supreme Court overturns the ACA's pre-existing condition protections," Kaiser said in releasing the poll. "In addition, half (52%) are 'very worried' they or a family member will have to pay more for coverage."

Some 72 percent of those polled are also in favor of keeping provisions that prohibit insurers from charging sick people more, which is also being challenged in the lawsuit.

Two-thirds of respondents said they are worried about paying for unexpected medical bills. That worry topped other sources of anxiety related to health care, including deductibles, drug costs and insurance premiums. Unexpected medical bills also worried respondents more than paying for housing, transportation or monthly utility bills.

Thirty-nine percent of insured adults who are between 18 and 64 years old said they have received an unexpected medical bill in the past year, according to the survey. Half of those who received an unexpected medical bill said it was less than $500 while 13 percent said their surprise bill was more than $2,000.

President Donald Trump's tactics to lower drug prices by publicly shaming them on Twitter drew a partisan response with 67 percent of Republicans saying his strategy will be effective and 74 percent of Democrats saying it won't work.

The majority of independent voters surveyed, 57 percent, agreed with Democrats.

Roughly 38 percent of Americans are either "very" or "somewhat" confident Trump can deliver on his promise of lower prescription drug prices, according to the poll.