Trailing in the Democratic presidential race, Bernie Sanders has one last gambit. He wants to persuade the party’s superdelegates—officeholders, luminaries, and party officials who can vote at the convention—that he’s the Democrats’ best hope to win the general election. Never mind that Hillary Clinton has won more votes and elected delegates. “There are a lot of delegates out there who are looking at the general matchup,” Sanders argued Sunday on CNN. “And what they’re seeing in polls is that Bernie Sanders is running a lot stronger against Donald Trump than is Hillary Clinton.”

It’s true that Sanders does better than Clinton in hypothetical matchups against the Republicans. Currently, Sanders outperforms Clinton by more than seven percentage points against Trump, and by nearly nine points against Ted Cruz. But that’s not because Sanders is the stronger nominee. It’s because Republicans haven’t yet trashed him the way they’ve trashed Clinton. Once they do, his advantage over her would disappear.

In recent days, several writers—Sahil Kapur in Bloomberg Politics, David Corn in Mother Jones, Greg Sargent in the Washington Post, Ed Kilgore in New York, and others—have sketched this argument. But is it true? Polls suggest it is. A concerted attack on Sanders’ weaknesses would hurt him badly in a general election. Here’s how it would look.

The problem with current polls that test Sanders against Trump or Cruz is that they don’t capture the effects of the fall campaign. As Harry Enten points out in FiveThirtyEight, early general-election polls in previous cycles were predictively worthless. Early in the 2000 election, for instance, George W. Bush led Al Gore by 12 percentage points. “Bush, then the Texas governor, burst onto the national scene with relatively little negative media scrutiny,” Enten observes. Between December 1999 and November 2000, as the scrutiny intensified, Bush’s net favorability fell 27 percentage points. He ended up losing the popular vote.

The best way to account for this kind of damage is to conduct a campaign within a poll. That sounds perverse, but campaign pollsters, unlike media pollsters, do it all the time. It’s called message testing. Here’s how it works: You’re running against another candidate. There are a lot of bad things you could say about him. You want to pick the message that will hurt him most and hurt you least. So you call up a bunch of people and ask them how they’re planning to vote. Then you try out the various messages you’re considering. After each message, you ask the person on the phone to what degree this statement makes her less likely to support your opponent. When you’re done, you ask her once more how she’s planning to vote, given the information you’ve provided. Congratulations: You’ve just conducted a campaign in a poll. You’ve ascertained how the election might turn out, depending on how you go after your opponent.

That’s what a pro-Clinton phone bank did to Sanders two months ago. Thanks to a voter who recorded the call and passed it to ABC News, you can listen to the whole spiel. First the caller asks the voter which candidate he’s planning to support. Then she reads talking points from each candidate and asks the question again. Then she tries out some pro-Clinton and anti-Sanders messages. “Next, you’re going to hear some statements that someone could make about Bernie Sanders,” she says. “After each one, please tell me how much it concerns you.” One statement is: “Bernie Sanders is making big campaign promises that will cost up to $20 trillion. The New York Times said his plans are not realistic. Other independent experts said his plans are unworkable and dead on arrival in Congress.” Another statement is: “Bernie Sanders’ plan is to replace Obamacare and put all Americans into a whole new health care system. His plan would force 70 percent of Americans to pay more for health care through higher taxes. Sanders himself said he will raise taxes.”

That’s what a general-election campaign against Sanders would look like—except it would be much, much worse. Republicans would rip Sanders as a big-spending, big-taxing socialist. They have plenty of ammo. They could quote the 2015 letter in which Sanders urged President Obama to “raise revenue” through “executive action.” They could dig up quotes from decades ago, in which Sanders called himself “clearly anti-capitalistic,” complained that U.S. interventions in Latin America “have been for the benefit of large corporations,” and praised communist countries as culturally superior. “Contrast what the young people in China and Cuba are doing for themselves and for their country as compared to the young people in America,” Sanders argued in 1976.

Republicans could hammer the back-seat foreign policy Sanders conducted as a mayor in Vermont: going to Cuba to seek a meeting with Fidel Castro, visiting Lenin’s tomb in the Soviet Union, and traveling to Nicaragua, where he met with Sandinista leader Daniel Ortega and praised the country’s cultural minister as a “hippie” whose government was “teaching poetry not only to peasants and to workers but in the military.” They could go after Sanders’ countercultural mockery of “respectful clerks, technicians and soldiers.” They could rehash his attacks on compulsory schooling, dairy laws, and fluoridation, or his Freudian analysis of napalm use in Vietnam, or his advocacy of public toddler nudity and genital touching as cures for porn, or the sexual quackery through which he attributed breast cancer and cervical cancer to orgasm deficiency and capitalist conformity.

Basically, if you were designing the perfect target for Republicans—a candidate who proudly links socialist economics to hippie culture, libertinism, left-wing foreign policy, new-age nonsense, and contempt for bourgeois values—you’d create Bernie Sanders. Clinton could have attacked these weaknesses in the primary—her supporters had an opposition research file on Sanders’ “associations with communism”—but she didn’t. In a general election, Republicans wouldn’t hesitate.

Would a GOP assault along these lines hurt Sanders? Absolutely. Start with his spending plans. Two months ago, an Associated Press-GfK poll asked Americans about Sanders’ proposal to replace “the private health insurance system … with a single government-run and taxpayer-funded plan” that “would cover medical, dental, vision, and long-term care services.” A 39 percent plurality favored the idea. Then the poll asked people whether they’d still support the plan if it meant “your own taxes would increase.” Suddenly, the plurality disappeared: Only 28 percent still favored the plan; 39 percent opposed it. When the poll mentioned that people would have to “give up other coverage like employer coverage” as part of the government-run system, again, 39 percent opposed it, while only 28 percent supported it.

Surveys by Vox and Morning Consult got similar results. In late January, 54 percent of registered voters said they would support “a single-payer health care system, in which all Americans would get their health insurance from one government plan that is financed by taxes.” Fifty-eight percent said they would support “the government using taxes to pay tuition at public colleges and universities in order to make college free for students.” But in April, when the same pollster asked voters how much they were willing to pay each year in additional federal taxes to fund these programs, only 15 percent and 17 percent, respectively, were willing to pay more than $1,000 for the health care plan and the free college system. “That’s well short of how much more the average taxpayer would pay under [Sanders’] tax plan,” Vox noted.

These polls show what would happen in a general election: Once Republicans focus attention on the per capita cost of Sanders’ health care plan, voters would turn against it. Sanders would fight back, noting that a single-payer plan could reduce premiums to make up for the tax increase. But Vox details elements of Sanders’ plan—a 2.2 percent surcharge on incomes and a 6.2 percent earnings tax levied on employers and passed through to workers—that make it unlikely Sanders could stay within the limit of what people are willing to pay.

Republicans wouldn’t just expose the cost. They’d also reframe the debate around the role of government. Sanders would argue that corporations are the greater menace—and he’d lose. The January Vox poll asked voters, “Which do you think is a greater potential threat to the country’s future?” Twenty-seven percent of respondents picked “Big Businesses.” Fifty-eight percent picked “Big Government.”

Politically, Clinton’s approach is smarter. A few months ago, Gallup asked Americans: “Do you think it is the responsibility of the federal government to make sure all Americans have healthcare coverage, or is that not the responsibility of the federal government?” A bare majority, 51 percent to 47 percent, said it was a federal responsibility. But Gallup also asked: “Which of the following approaches for providing healthcare in the United States would you prefer—a government-run healthcare system, or a system based mostly on private health insurance?” A slightly larger majority, 55 percent to 41 percent, preferred a private system. So Republicans would probably lose a debate against Obamacare. But they’d win a debate against Sanders’ single-payer plan.

Sanders’ explicit socialism would help Republicans broaden this critique into an all-out scare campaign about a government takeover. There are lots of reasons to believe such a campaign would succeed. In a national Reason-Rupe poll taken two years ago, capitalism had a net favorable rating of 55 percent to 38 percent. Socialism had a net unfavorable rating of 58 percent to 36 percent. Last year, Gallup asked Americans: “If your party nominated a generally well-qualified person for president who happened to be socialist, would you vote for that person?” Forty-seven percent of respondents said they would, but 50 percent said they wouldn’t. Every other kind of candidate tested in the Gallup poll—black, Mormon, gay, Muslim, atheist—garnered majority support, probably because the question stipulated that the candidate had already been nominated by “your party.” Only a socialist nominee was rejected. Among Democrats, a socialist was the only type of nominee who didn’t get 60 percent support.

Sanders supporters discount such polls, noting that Sanders calls himself a “democratic” socialist. That stipulation helps, but not enough. A January YouGov poll asked Americans: “Bernie Sanders has described himself as a ‘democratic socialist.’ Does this make you more or less likely to support him, or does it make no difference either way?” Twelve percent of respondents said more likely; 18 percent said less likely. Among independents, 8 percent said more likely; 15 percent said less likely. That’s in addition to the 39 percent of all respondents who said it made no difference because “I wouldn’t support him anyway.” Polls in swing states show the same pattern. In New Hampshire, 20 percent of likely Democratic primary voters said a “Democratic socialist” president would be unacceptable. In Virginia, 52 percent of all voters said they’d be less likely to vote for a presidential candidate who “was a Democratic-Socialist.” The phrase was a net loser with every audience. Two out of three Democrats didn’t care, but among those who did, the percentage who said they’d be less likely to vote for such a candidate (15 percent) slightly exceeded the percentage who said they’d be more likely (12 percent).

After beating up Sanders for his domestic socialism, Republicans would turn to his dalliances with communist regimes. Five years ago, in a Rasmussen survey, 77 percent of likely voters said the American system of politics and economics was “morally superior to communism.” Eighty percent said the American system was “better for middle class workers.” (Ten percent said communism was better.) Fidel Castro’s most recent favorable rating in a poll of Americans, taken two years ago, was 6 percent favorable and 81 percent unfavorable. In a Gallup poll taken two months ago, China’s unfavorable rating was 52 percent, Russia’s was 65 percent, and more than 85 percent of Americans said both countries were critical or important military threats to the United States.

Sanders could point out that he made the right call on Iraq. But that wouldn’t help him against Trump, who also criticized the war. As for Sanders’ comments about compulsory schooling, genital touching, and carcinogenic chastity, those views have never been polled, because they’re too flaky. It would be a cheap shot to bring them up, since they’re decades old, but that wouldn’t deter Republicans. What might hold Republicans back from the flaky stuff is that they don’t need to get personal to kill Sanders. They could kill him just by talking about his health care takeover, his spending plans, his taxes, his socialism, and his admiration of totalitarian regimes.

Instead, Republicans face a showdown with Clinton. After three presidential elections, eight years in the White House, eight in the Senate, and four as secretary of state, she’s one of the most thoroughly investigated people in American history. Everyone’s heard about Whitewater, Benghazi, her Wall Street speeches, and her email server. That’s why she does worse than Sanders in general-election polls. But it’s also what depresses Republican strategists. They’ve subpoenaed everything they can find on her, unloaded all their oppo, and she still wins. Their only hope is a fresh piece of meat, an alternative Democratic nominee who looks clean to liberals but is loaded with unexploited vulnerabilities and is easier to caricature as a wild-eyed socialist. Someone like Bernie Sanders.

Read more Slate coverage of the Democratic primary.