Jon Cowan is president and Jim Kessler is executive vice president for policy at Third Way, a center-left think tank.

In the lead-up to the Iowa caucuses, Sen. Bernie Sanders (I-Vt.) is arguing that he is the Democratic candidate most likely to beat President Trump. He has touted his electability in speeches and interviews and on social media, and his campaign has said it welcomes a debate on electability.

We should have that debate, because the fact is that the United States has never elected anyone as president who is as far left as Sanders. The only modern Democratic nominees approaching Sanders’s ideological views were former vice president Walter Mondale in 1984 and then-Sen. George McGovern in 1972. Together, they won a scant 30 electoral college votes and lost the popular vote by a combined 35 million votes. Mondale’s wipe-out was the biggest electoral college loss in U.S. history.

For those who say these landslide races were ages ago, and that Donald Trump is no Ronald Reagan, fair enough. How about December 2019? That is when Sanders clone Jeremy Corbyn got routed by Trump clone Boris Johnson in the British parliamentary elections, sending the Labour Party to what some said was its worst defeat in more than 80 years. Corbyn, who Sanders predicted would lead his party to a resounding victory and “should be a lesson for the Democratic Party,” tanked. He “literally repelled voters,” former Labour MP David Milliband wrote after the debacle.

For Sanders to have a chance of winning, let alone proving to be the most electable as he claims, Americans would suddenly have to become comfortable with socialism. That would be quite a change, since, as of three months ago, socialism was viewed negatively in the United States by a 13-percentage-point margin (55 percent negative, 42 percent positive), according to the Pew Research Center.

Sanders’s team says that no matter who is nominated, Republicans will smear that Democrat with the “socialism” label. That’s whistling past the graveyard. Democrats have easily batted this spurious charge aside, because they ran on a mainstream progressive agenda. Sanders won’t and can’t. He has embraced the socialist label his entire political life, and his agenda, as he likes to point out, is far beyond anything Democrats have proposed on the national stage.

The centerpiece of that agenda is Medicare-for-all, a politically toxic proposal that represents the only way Democrats could fumble away their health-care advantage over Trump. Democrats’ pledge to preserve and expand on President Barack Obama’s Affordable Care Act was a decisive factor in flipping the House from red to blue in 2018. Sanders would do the opposite, ditching Obamacare in favor of his single-payer, government-run proposal. This plan has steadily lost popularity over the past year and fares particularly poorly in the make-or-break “Blue Wall” states.

Electability matters down the ballot as well. If Sanders is the nominee, he will face the spectacle of Democrats in swing states and districts running from his agenda, not toward it. To date, Sanders does not have a single endorsement from a lawmaker on the Democrats’ Frontline list — the House Democrats facing tough races, many in districts Trump won in 2016. That is not an accident.

The Sanders agenda won’t sell there, and elected Democrats running for their political lives in these critical states and districts will sprint from a set of plans that costs between $60 trillion (the cautious estimate) and $97 trillion (the estimate Republicans will use) over the next decade. These Democrats will balk at an agenda that doubles the size of government. They will say no to the middle-class tax increases already being proposed by Sanders and the massive deficits he could create because his tax plans cover only a sliver of his costs.

In 2017, Sanders wrote in the New York Times that, to win in 2018, Democrats should run on an agenda that was unapologetically far to the left. Led by then-Minority Leader Nancy Pelosi (D-Calif.), they did exactly the opposite. When the dust settled on Democrats’ landslide victory, Sanders’s political organization could not claim a single flipped seat in the House, while the moderate New Democrat Coalition claimed 31 of the net 40 red-to-blue wins.

Sanders is truly an authentic politician. That helps explain why some early national polls show him competitive in a head-to-head race against Trump. But at about this time in 1984, a Gallup poll had Mondale in a dead heat with Ronald Reagan. Eleven months later, after Mondale’s agenda was fully litigated, Reagan won 59 percent to 41 percent.

Let’s be clear: Sanders is not only far less electable against Trump than is Joe Biden, but he’s also less electable than Sens. Elizabeth Warren (Mass.) and Amy Klobuchar (Minn.), former mayors Pete Buttigieg and Mike Bloomberg, and just about anyone else who qualifies for a debate stage or is registering in national polls. Of course, loyal Democrats, including us, would absolutely vote for Sanders against Trump. But the Sanders agenda won’t stand up to scrutiny for a lot of people who are open to ousting him. That’s the definition of unelectable.

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