As Republican presidential hopefuls vie to persuade voters that they are uniquely qualified to lead America, they are united in their opposition to one thing: the Affordable Care Act. Major candidates so far have already tried or have promised to repeal the landmark health care law, and opposing it promises to be a popular selling point in the 2016 elections.

Behind all the rhetoric, however, are several thornier issues, including whether candidates could offer a feasible alternative to the Affordable Care Act, often referred to as Obamacare, and whether they’d be able, as president, to fulfill campaign promises to repeal the law, which experts describe as increasingly entrenched in the American health care system. Despite these obstacles, voicing opposition to Obamacare is all but a given for GOP candidates, especially in advance of the 2016 primaries, which tend to attract far-right voters.

“Getting rid of [Obamacare] is going to be a key issue,” said Dan Judy, a Republican pollster with North Star Opinion Research, which is working on Sen. Marco Rubio’s presidential campaign. “Candidates are going to look at this and say, ‘This is bad policy. Here’s a law you don’t like. If Hilary Clinton is elected, it will stay; if I’m elected, it will go.’ ”

So far, declared and expected candidates have fervently and vocally opposed Obamacare. “Imagine in 2017 a new president signing legislation repealing every word of Obamacare,” Sen. Ted Cruz of Texas told an audience at Liberty University in Lynchburg, Virginia, in announcing his candidacy for president. Cruz also spearheaded efforts in 2013 to defund Obamacare that ultimately led to a government shutdown.

Florida Sen. Marco Rubio, another candidate, was also a part of those efforts in 2013. Most recently, in March, he proposed a plan to replace Obamacare if the government loses in the Supreme Court case King v. Burwell, which could cost residents of certain states federal subsidies crucial in offsetting the cost of health insurance. A decision on the case is expected in June or July.

Former Florida Gov. Jeb Bush hasn’t officially announced that he’s running, but he has called for replacing Obamacare, and in March, he declared Obamacare “the greatest job suppressor” after 2008.

Kentucky Sen. Rand Paul, a declared candidate, wrote on Facebook in August, "I won't rest until ObamaCare is 100% repealed." He also, however, acknowledged that it would be difficult to repeal the legislation.

Democratic candidate Hillary Clinton, on the other hand, has been a staunch supporter of Obamacare. "Repeal of the ACA would let insurers write their own rules again, and wipe out coverage for 16 million Americans," she wrote on Twitter in March.

A New Health Care Landscape

Just because candidates are clamoring to undo Obamacare, however, doesn’t mean they can. Not only is the law increasingly rooted in the American health care system, but any attempt to repeal the ACA would also likely require Republicans to keep or win a certain number of seats in Congress in the 2016 elections, if a Republican president was behind it.

“You’ve got a lot of people who have coverage that they’re growing used to,” said Michael Sparer, a professor of health policy and management at the Mailman School of Public Health at Columbia University in New York. “It doesn’t mean they’re happy with their coverage … but they’ve got coverage." Insurance companies, employers, hospitals and doctors have all begun adapting to the Affordable Care Act, and “to simply pull the plug on that, I think there’s going to be a lot of resistance,” Sparer added.

Promises to eliminate Obamacare must come with actual alternatives to the law, experts pointed out. “The best way for potential Republican candidates to argue for repealing Obamacare would be with a relatively detailed alternative health reform plan,” Rick Mayes, an associate professor of political science and co-director of the healthcare studies major at the University of Richmond in Virginia, said. “In other words, suggest a better model or path for reform.”

Judy, the Republican pollster, said the same. “What do we replace it with?” he asked. Having not just a plan to repeal but also something to replace Obamacare would be key, he added, even though he said it was too early for candidates to have devised specific proposals for an alternative.

Repealing the law would be contingent upon other outcomes in the 2016 elections. Republicans would have to maintain a majority in the House and would probably have to expand their majority in the Senate, and so in terms of promising to repeal Obamacare, “whether or not this can be kept based on the political reality remains to be seen,” Judy said. 

A Republican Requirement

“Repeal of the ACA has become simply a given for all Republican candidates,” Joseph White, a professor of public policy at Case Western Reserve University in Cleveland, said in an email. “It has become an article of faith among Republicans that ‘Obamacare’ represents everything that has gone wrong with the country."

The fact that candidates are competing for the Republican nomination first, instead of a general election, also affects the degree of fervor. “Any sort of primary draws the most partisan voters on both sides,” Sparer said. “Opposition [to Obamacare] resonates strongly with a large segment of the population, especially the more partisan Republicans, who are more likely to be engaged and active in the upcoming primaries."

There’s also the belief that supporting Obamacare could cost a candidate an election. In Colorado during the 2014 midterm elections, Republican Cory Gardner campaigned on a strong anti-Obamacare platform that included claiming that incumbent Democratic Senator Mark Udall had cast the deciding vote that passed Obamacare. Although the truth of that statement is disputed, Gardner ultimately unseated Udall, and so for GOP candidates, anything less than outright opposition to Obamacare may not be an option.

Public opinion on what the Affordable Care Act provides or has achieved so far is divided. In March, a Kaiser Health Tracking Poll found that 41 percent of respondents viewed the health care law favorably, while 43 percent viewed it unfavorably. Nevertheless, some surveys also suggest that Americans generally favor changing Obamacare instead of repealing it entirely, with more than half of respondents in a Rasmussen poll in December saying they would rather have the law improved and only 30 percent supporting a full repeal.

But despite the law’s apparent lack of popular support, the rate of uninsured people in the U.S. is at an all-time low of 11.9 percent, a poll released Monday showed, and experts suggest that one reason Americans oppose the law is that they don’t fully understand it. In the middle of 2013, before the health insurance exchanges established by the law went into effect, an estimated 18 percent to 20 percent of American adults lacked health insurance.

Pete Damiano, director of the Public Policy Center at the University of Iowa, said that according to the center’s surveys of consumers, “when you ask them about the various pieces and parts of the Affordable Care Act, like keeping people on their parents’ plans … there’s pretty much universal support,” Damiano said. It’s when people are asked about their feelings about the law overall that they start to dislike it, he explained, and “even though they like the pieces and parts, because of the political rhetoric, there’s a lot of confusion.”