The Affordable Care Act has been featured prominently in previous elections, often working in Republicans favor. Now Democrats are trying to turn the tables, campaigning on a piece of the law that the public has embraced.

After years of intense opposition, public opinion on the controversial law appears to have shifted, in large part because the ACA requires insurers to cover pre-existing medical conditions. But that and other elements of the law could be jeopardized by a Republican lawsuit involving 20 states. 

Wisconsin is one of the lead states in the lawsuit that argues the ACA should be scrapped because Congress got rid of the penalty for not having insurance when they passed the GOP tax cut bill. The federal lawsuit hinges on the individual mandate, the requirement that everyone have insurance. It’s the least popular part of the ACA, also known as Obamacare.

"Personally, I don’t think the government should mandate that — that’s none of their business. What if I don’t want to buy it? And I’m not partaking in benefits of it?" asked 54-year-old Robert Zettle of Madison who describes himself as conservative.

Even liberals like 23-year-old Zach Young of Fredonia understand why the requirement to have insurance rubs some people the wrong way. But Young says there’s a reason it's there.

"I would also not get insurance if I had that option. However, if you stop requiring people to get insurance, it prevents the pool of money from being there to help everyone else," explained Young.

People may not like the mandate, but they do like other parts of the law. A recent poll by the Kaiser Family Foundation shows 50 percent approve of Obamacare overall. That rises to 75 percent when people are asked about the law's protections for people with pre-existing conditions.

The GOP lawsuit would get rid of those safeguards and it’s a point Democrats are trying to drive home in their campaigns. Ads on the topic have continued to surface including one from A Stronger Wisconsin featuring a mother with cancer, and another from Democratic U.S. Sen. Tammy Baldwin featuring a nurse.

Both of the women in the ads have medical conditions for which it would have been difficult to obtain insurance before the ACA. 

An estimated 25 percent of Wisconsinites have a pre-existing condition that might not be covered if Obamacare is struck down, according to the Kaiser Family Foundation.

Gov. Scott Walker says he supports a bill that would cover pre-existing conditions at the state level. But the bill would still let insurance companies impose lifetime caps on coverage. The Assembly approved the bill, but it never made it on the books because the Senate didn’t pass it.

At the same time Walker was pushing the state plan he said would protect pre-existing conditions, the governor also took steps that would undermine those protections at the federal level. It was Walker who gave the go-ahead for Wisconsin Attorney General Brad Schimel's lawsuit to overturn the ACA.

Democratic attorney general hopeful Josh Kaul is trying to use that against Schimel.

"The state, Brad Schimel, is arguing that we should strike down protections for pre-existing conditions, the guarantee that young adults can stay on their parents coverage," said Kaul.

But Schimel says Obamacare is unconstitutional and didn’t do what it promised.

"We want this power to go back to the state of Wisconsin. To let legislators and leadership in Wisconsin determine what’s best for Wisconsin," Schimel said. 

Schimel and other Republicans who support the lawsuit contend there are better ways to run a health care system. And they’re hoping voters see it that way too.

But Republicans in Washington weren’t able to muster the votes to pass a health plan replacing Obamacare — in large part because of a public backlash over their plan's lack of protections for pre-existing conditions.

Speaking at the state Democratic convention in June, U.S. Sen. Tammy Baldwin told party activists they won that fight.

"You own that defeat of that cynical bill. Know your power. That was you. And that’s what it's going to take to win this next election," Baldwin said.

It’s a contest where the political parties find themselves fighting over a familiar issue. Only the ground may have shifted since the last election.

This story is part of a three-part election season series on where Wisconsin's candidates stand on health care. Some of the interviews in this story came from WPR's special series Beyond The Ballot, a project dedicated to finding out what Wisconsinites care about. Read Part 2 and Part 3.