President Donald Trump, who campaigned on repealing and replacing the Affordable Care Act, signed an executive order Thursday to unwind the health care law, claiming it will make lower-premium plans more widely available.

"This is promoting health care, choice and competition, all across the United States," said the president. "This is going to be something that millions and millions of people will be signing up for and they're going to be very happy. This is going to be great health care."

Critics say it would also mean fewer healthier people would enroll in the exchanges, raising premiums for the sicker people left remaining. Senate Minority Leader Charles Schumer said the executive order will "probably be challenged in court." 

"It's going to hurt the people and it's going to hurt him, so I've advised him not to do that but rather work with us to make it better," said Sen. Schumer during an unrelated news conference in Rockville Centre. "Don't just sabotage it because he's mad at it." 

Rachel Siehs, a 29-year-old cancer survivor, says she couldn't have afforded her treatments without help from "Obamacare." She worries any change could mean she won't get coverage because of her previous lymphoma diagnosis. 

"People could say 'We don't really want to cover you because we know we have to spend $10,000 year for your continuing  [health care] ," she told News 12 Long Island. "…That's what's scary."