Bernie Sanders sits second in the crowded Democratic primary field, but the Vermont senator’s campaign is confident he’s leading the conversation on one of the race’s top issues.

During a call with reporters Monday, senior campaign adviser Jeff Weaver said the focus of the Democratic presidential primary shifted to health care after July debates in Detroit. Health care proposals have become a point of distinction between moderates and progressives in the race, and Sanders fended off critics of his “Medicare for All” plan for much of the debate.

Sanders’ universal healthcare proposal is a central policy promise of his 2020 campaign. The Vermont senator argues Americans are paying too much for insurance that doesn’t cover their needs, leading to worse health outcomes and financial hardship.

His solution is to guarantee health care as a human right provided by the government, eliminating a profit motive in the health care industry. Sanders introduced a senate bill in April, which was cosponsored by four Democratic rivals, that would end the private insurance market in favor of a single-payer government-run system.

Sanders faces a double-digit gap in support between himself and Democratic presidential front-runner Joe Biden. However, the campaign cited an August Morning Consult/Politico poll showing Sanders is the most trusted candidate to handle voters’ health care concerns.

Republicans have tried to frame the election as a fight against Democratic attempts to impose socialist policies. Michigan Republican Party Chair Laura Cox called Sanders’ Medicare for All proposal a “socialist scheme” after the Detroit debate.

Ben Tulchin, a pollster for Sanders’ 2016 and 2020 campaigns, said Medicare for All is growing in popularity across the country. However, support for a government-run system drops when voters are told it could require them to pay more in taxes or eliminate private health insurance companies, according to the Kaiser Family Foundation.

Support for Medicare for All dropped in the Morning Consult poll from 53% to 46% when respondents were told the government-run health system would diminish the role of private insurers. It increased to 55% when voters were told they would be allowed to keep their preferred doctors and hospitals.

“The fact of the matter is, tens of millions of people lose their health insurance every single year when they change jobs or their employer changes that insurance," Sanders said in Detroit. “If you want stability in the health care system, if you want a system which gives you freedom of choice with regard to a doctor or a hospital, which is a system which will not bankrupt you, the answer is to get rid of the profiteering of the drug companies and the insurance companies, move to Medicare for all.”

Biden is seeking to grow the number of people covered by the Affordable Care Act instead of eliminating the private insurance market. He argued on the debate stage that it’s better to give people the option or buying into government-run health insurance instead of mandating it, and promised his solution is much 1/30th the cost of Medicare for All proposals pushed by his rivals.

Sanders argues the single-payer system would result in overall savings. A tax hike would be needed to cover part of the cost, but Sanders said Americans would see fewer out-of-pocket costs and also calls for taxes on employers and taxes on high-income households.

Potential methods to finance the bill released by Sanders’ office include a 4% “income-based premium” on households making more than $29,000 per year. By replacing premiums to private health insurance companies, Sanders expects the average family making $50,000 to save $4,400 a year.

Tulchin said voters name health care as the most important issue in the Democratic primary.

Richard Czuba, founder of Glengarrif Group Inc., disagrees.

“The preeminent issue for Democrats is defeating Donald Trump,” Czuba said.

Trump and Democrats identified Michigan as a key battleground after the formerly blue state voted from Trump in 2016. Sanders won the 2016 Democratic primary, but ultimately lost the nomination to Hillary Clinton.

Early primary polling shows Sanders beating Trump in Midwest battleground states, including Michigan.

Weaver said Sanders’ success is due to months of intense campaigning on health care. A July campaign event saw Sanders cross the border into Canada from Detroit with a group of U.S. citizens in search of cheaper insulin.

Though there is broad agreement about the need to protect pre-existing conditions, Czuba said Michigan voters aren’t sold on Medicare for All.

In a Glengariff poll before the Detroit debate, 51% of likely Michigan voters opposed eliminating private insurance in favor of a Medicare for All plan. A majority of voters who identified as Democrats supported the idea (57.5%), but 53% of independents opposed it.

The poll of 600 likely voters was conducted by Glengariff Group on behalf of the Detroit Regional Chamber.

“Democrats support Medicare for all, but it’s by no means overwhelming support,” Czuba said.

Czuba said Democrats are split on the issue based on age. Voters over 40 years old have mixed opinions on eliminating private insurance, while voters under 40 are strongly in favor, he said.

“When it comes to Medicare for All, among older Democratic voters there is a hesitancy. There is a reluctance,” Czuba said.

Part of that could be due to older voters having a stronger relationship with employer-provided insurance companies, he said.

During the Monday press call, Sanders campaign co-chair Nina Turner pushed back against “talking points that this would hurt members of labor who have worked very hard to get that health care.” Turner, a former Ohio state senator, said employers can put the money used to pay for health care toward wages instead.

U.S. Sen. Tim Ryan, D-Ohio, clashed with Sanders on this point during the July debate in Detroit. An estimated 600,000 union members in Michigan would give up their private healthcare plans for government coverage.

“So here we are in Detroit, home of the United Auto workers,” Ryan said. “We have all our union friends here tonight. This plan that’s being offered by Senator Warren and Senator Sanders will tell those Union members who gave away wages in order to get good healthcare that they’re going to lose their healthcare because Washington’s going to come in and tell them they got a better plan.”

Ryan said Sanders can’t guarantee union members would keep benefits they fought hard to negotiate for. Sanders slapped the assertion down in one of the debate’s key moments.

“I do know it, I wrote the damn bill,” Sanders said.