Democrats are expressing outrage over the Trump administration's decision not to defend the Affordable Care Act in a new lawsuit, but the Obama administration similarly elected not to defend the constitutionality of the Defense of Marriage Act beginning in 2011.

In a brief filed in a Texas federal court Thursday night, Jeff Sessions' Justice Department agreed with the 20 GOP-led states bringing the suit arguing the individual mandate provision of Obamacare was unconstitutional. Republicans sought and failed to repeal and replace Obamacare in 2017.

House Minority Leader Nancy Pelosi called it a "cynical sabotage campaign" and a "stunning new low."

"Once again, Republicans are trying to destroy protections for Americans with pre-existing conditions," she said in a statement. "The Trump administration is perpetuating the same cruel vision of higher costs and less coverage that House Republicans voted for in the monstrosity of Trumpcare."

Sen. Bob Casey (D., Penn.), one of several Democrats seeking re-election in states President Donald Trump won in 2016, blasted the Justice Department's decision in a fundraising letter.

"The Trump administration is coming after the Affordable Care Act's protections for people with pre-existing conditions and it's time for us to draw a hard line," Casey said. "I'm mad as hell, and I'm ready to fight this with both fists up."

Democratic Reps. Bobby Scott (Va.), Frank Pallone Jr. (N.J.) and Richard Neal (Mass.) also criticized the decision in a joint statement. They are the top three Democrats on the House's health care committees.

"The Justice Department’s refusal to defend the Affordable Care Act in federal court is a stunning attack on the rule of law, the stability of our health care system, and Americans’ access to affordable health care," they said.

Democratic strategist Brad Woodhouse said the move was a means to "steal coverage from millions of Americans" and Trump's "most dangerous sabotage effort yet," according to the New York Times.

Pro-Obamacare University of Michigan health professor and former Justice Department attorney Nicholas Bagley savaged the decision on Twitter.

"I am at a loss for words to explain how big of a deal this is," he wrote. "The Justice Department has a durable, longstanding, bipartisan commitment to defending the law when non-frivolous arguments can be made in its defense. This brief torches that commitment."

The vice president of health policy at the left-wing think tank Center for American Progress called it a refusal to follow "bipartisan tradition,"

"In refusing to follow bipartisan tradition and defend the ACA in the U.S. federal court system, the Trump administration is nakedly admitting that it wants to eliminate protections for people with pre-existing conditions, breaking a promise that the president has made time and again," said Topher Spiro.

Yet in 2011, then-Attorney General Eric Holder announced he had been instructed by President Barack Obama to stop defending DOMA, the former President Bill Clinton-signed law federally defining marriage as between one man and one woman.

"After careful consideration, including a review of my recommendation, the President has concluded that given a number of factors, including a documented history of discrimination, classifications based on sexual orientation should be subject to a more heightened standard of scrutiny," Holder said. "The President has also concluded that Section 3 of DOMA, as applied to legally married same-sex couples, fails to meet that standard and is therefore unconstitutional. Given that conclusion, the President has instructed the Department not to defend the statute in such cases. I fully concur with the President's determination."

Section 3 of DOMA was declared unconstitutional in 2013 with the decision United States v. Windsor, and the law was fully invalidated by the landmark decision Obergefell v. Hodges, which ruled the right to marry for same-sex couples was protected by the 14th Amendment.