Former Vice President Joe Biden and U.S. Senator Kamala Harris gesture on the second night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 31, 2019.

"They don't have a lot of clarity [on health plans] after they get past Warren and Sanders and Biden," said Patrick Murray, director of the Monmouth University Polling Institute. "I don't think the debates last month helped at all."

Those who back a public health insurance option — the most popular solution among Democratic voters — have less clarity about who shares their views. About a third of public-option backers say Biden aligns with their health-care outlook, followed by Warren with 18%. (The senator does not support a public option).

More than a quarter, or 28%, of likely participants in the first-in-the-nation Iowa caucus say they do not know which candidate comes closest to matching their views on health care, according to a Monmouth University poll released Thursday. Supporters of a single-payer "Medicare for All" system have a clear idea of who shares their vision for health care. Among likely caucus participants who back the government-run universal health care system, 64% say Sen. Bernie Sanders shares their views, while 44% believe Sen. Elizabeth Warren aligns with them. Sanders and Warren back Medicare for All.

All of those details will be critical if a Democrat wins the White House and gets a chance to propose health-care reform. Still, a new poll suggests that despite the spotlight on health care, voters are struggling to understand the differences between candidates' plans.

In 15- and 30-second bursts, former Vice President Joe Biden and Sen. Kamala Harris sparred over their similar health-care plans. They wrangled over the cost of expanding insurance coverage. They argued over how long their plans would take to phase in. And they battled over how much they would do to limit co-pay costs.

Democrats argued about their health care plans for more than an hour during both nights of last week's presidential primary debates.

An array of state and national polls have found that voters see health care as the most important issue in the 2020 election. In Iowa — which will help to weed out candidates when it holds its caucus in February — 55% of likely caucus participants say health care is the most important issue in the presidential race.

Ahead of the Detroit debates last week, 83% of Democrats and Democratic-leaning independents said it was "very important" for candidates to talk about health care on stage, according to a Kaiser Family Foundation poll. Fifty-one percent of respondents said they wanted to hear Democrats talk about how their plans differ from their primary competitors' proposals. Thirty-eight percent said they hoped to hear Democrats discuss their differences with President Donald Trump.

But it can be difficult even for the most engaged or well-educated voters to grasp the complexities of health-care reform.

Democratic contenders have split into two rough groups: those who want a single-payer plan to insure every American and those who seek improvements to the Affordable Care Act to gradually move toward universal coverage.

As the leader in most national and state polls, Biden is the most prominent contender pushing to give Americans the choice to buy into a government plan. The former vice president and others with similar plans have warned against scrapping the private insurance industry — which Medicare for All would do.

Sanders has led the charge for Medicare for All after helping to bring it into the political mainstream. Proponents say it will cover everyone while bringing down overall costs, even though it will bring tax increases for many Americans.

Some officials felt the health-care discussion at the debates fell short. Rep. Debbie Dingell, a Detroit-area Democrat and co-chair of the House Medicare for All Caucus, told CNBC last week she wants to see her party better explain health care and "talk in simpler terms."

Voters appear to have a tough time drawing distinctions between the plans of candidates like Biden, Harris, South Bend, Indiana, Mayor Pete Buttigieg and Sen. Amy Klobuchar, Monmouth's Murray said. All of those presidential hopefuls back some version of a public health-care expansion that stops short of abolishing private insurance.

Still, getting voters to understand specifics of a health plan may not matter much in a primary election, said Robert Blendon, a Harvard University public health professor who studies public opinion. He said promises to pursue a broad idea or vision resonate more than a plan's details do.

"In the primaries, it's really your commitment to the issue and the sense you give that you're going to fight for it," he said.

Specifics of a policy plan tend to matter more when it has a real chance of becoming law, Blendon added. He pointed to the Republican push to repeal and replace the Affordable Care Act as an example.

Opposition to Obamacare mounted after it became law in 2010. Resistance to it helped Republicans triumph in the 2010 and 2014 midterms.

Then, Trump and his GOP rivals all ran on scrapping Obamacare in the 2016 presidential primary — without much of a plan to replace it. When voters eventually saw what a Republican alternative would look like in 2017, support for the ACA grew — and opposition to repeal helped Democrats win the House last year.

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