(CNN) President Donald Trump's latest escalation of his years-long bid to kill Obamacare has given Democrats running for president in 2020 a new opening to assail Trump -- and to sell their own visions of expanded health coverage.

The move by the Justice Department -- telling a federal appeals court on Monday that the Affordable Care Act should be struck down in its entirety -- shifts the political lens back to the issue that helped bolster Democratic victories in the 2018 midterms: health care -- and specifically, Republican efforts to undercut President Barack Obama's signature law.

Across the board, Democratic contenders lambasted the Trump administration's move.

"It's about playing politics with people's public health," Sen. Kamala Harris from California said on MSNBC.

Sen. Bernie Sanders of Vermont tweeted that Trump's administration wants to "throw millions of Americans off health insurance and put lives at risk. We will fight back."

Pete Buttigieg, the mayor of South Bend, Indiana, said on Twitter that for those who benefit from the Affordable Care Act, "it is now the official position of the White House to take away your health coverage, with no sign of a plan to help you if they win and you lose."

And Massachusetts Sen. Elizabeth Warren tweeted, "Health care is a basic human right, and we fight for basic human rights." Former Texas Rep. Beto O'Rourke vowed on Twitter to "protect the care of those whose lives depend on it."

Of course, the 2020 field itself is divided on how to expand health care access, with some candidates advocating single-payer programs that would eliminate private insurance and others seeking to allow people to buy into Medicare.

But by making another push to kill Obamacare, Trump and his administration have given candidates a set of health care policies around which they can coalesce -- including ensuring coverage for those with pre-existing conditions, banning yearly lifetime limits and allowing children to remain on their parents' insurance until age 26.

On debate stages and in town halls, the entire Democratic field is likely to be "spending a good chunk of their time talking about how they want to maintain and improve health care for all Americans," said Anne Caprara, a veteran Democratic strategist who is now Illinois Gov. J.B. Pritzker's chief of staff. "And that's an enormous win for Democrats overall."

"There's a conversation going on about Medicare for All and public options, but I think, frankly, people spend way more time focusing on that on Twitter than they do out in the electoral base," she said. "The Affordable Care Act is popular with Democratic voters -- very popular. Nobody wants to see it repealed."

Angel Padilla, policy director of the progressive political group Indivisible, said Tuesday's move would animate the Democratic base and send "another signal that this is why the 2020 election matters.

"It's about people's lives and it's about health care," he said.

Trump's latest effort to undo Obamacare will also raise the stakes of Democrats' intra-party debate over whether to pursue a single-payer health system that eliminates private insurers or set that long-term goal aside in favor of incremental steps toward universal coverage.

A Sanders aide said the administration's move elevates what the Vermont senator's camp saw as one of his top issues.

"I don't know what it says about other candidates, but I think that it plays to his strengths as a candidate because he has a very clear message about health care and about the need to guarantee health care to every American as a right, not a privilege," the Sanders aide said.

The Sanders camp's view is that a world in which health insurers have a profit-making incentive is not sustainable.

"As long as you have private insurance companies as a part of that equation, you're going to have a system that is not purely interested in making people healthy and doing it in the most cost-effective way possible," the aide said.

Supporters of Medicare for All argue that with Senate Majority Leader Mitch McConnell and Republican-appointed judges in the way, anything short of a revolutionary change would have little hope of advancing.

Other Democratic presidential candidates, though, have argued that a more narrow approach is all that's politically feasible.

O'Rourke has touted legislation by Illinois Rep. Jan Schakowsky and Connecticut Rep. Rosa DeLauro that would move everyone who doesn't already have private insurance from their employers into Medicare -- and allow those who do have private insurance the option of buying into Medicare instead.

Sen. Amy Klobuchar from Minnesota said in a recent CNN town hall that she wants to "build on the work of the Affordable Care Act."

She said Medicare for All "could be a possibility in the future," but that she is looking for "something that will work now."

Whatever their differences, Democrats are unanimous in opposing Trump's pushes to undercut Obamacare, said Karen Pollitz, a senior fellow at the Kaiser Family Foundation.

"But going forward and now, there is acknowledgment that there are shortcomings with the current law. Not everybody has coverage. Not everybody is eligible for help who needs it. We've got other instability that has been initiated or aggravated by the administration's actions and by the actions of state officials that are hoping to undo or destabilize the law," Pollitz said.

"This is going to be a prominent issue throughout the campaign: what direction makes sense. And also, is one direction the answer?" she said. "Do (the Democrats) define themselves by this one approach or could they lay out a path that perhaps would have some incremental steps along the way?"