Sen. Bernie Sanders (I-Vt.) introduces the Medicare for All Act of 2019 with Sens. Kirsten Gillibrand (D-N.Y.) and Jeff Merkley (D-Ore.) during a news conference last month in Washington. (Mark Wilson/Getty Images)
Opinion writer

In the wake of the enormous gains in the House in the 2018 midterms, the moderate Democratic group Third Way reminded us that it wasn’t the far-left candidates who delivered the House majority:

The moderate New Democratic caucus in the U.S. House endorsed 37 candidates in primary races, and 32 earned the nomination — an 86 percent win rate. By contrast, Our Revolution, the grass-roots organization founded and run by Bernie Sanders’s backers, had a win rate under 40 percent in the primaries. Once the general election rolled around, 23 New Democrat-backed candidates flipped House seats to help gain the majority, while not a single Our Revolution-endorsed candidate captured a red seat. Zero.

Speaking of zero, our team watched every one of the 967 ads that Democrats ran in competitive House districts since Labor Day, and just two candidates mentioned either Medicare-for-all or single payer, and of those, neither won.

Lest you think that Democratic moderates couldn’t turn out young voters or nonwhite voters, census data showed soaring participation by both categories of voters: “Among 18- to 29-year-olds, voter turnout went from 20 percent in 2014 to 36 percent in 2018, the largest percentage point increase for any age group — a 79 percent jump. ... Voter turnout increased among non-Hispanic Asians by 13 percentage points, a 49 percent increase.” And African American turnout increased by 11 percent.

While moderate candidates showed the ability to energize a diverse electorate, the same cannot be said for the far left. The far left talks a good game on diversity, but that segment of the electorate is among the least diverse:

In its groundbreaking 8,000-person survey, More in Common found that “progressive activists” in the electorate are 92 percent white. Of all the “political tribes” it identified in its report on “The Exhausted Majority,” only “devoted conservatives” (at 94 percent) are more consistently white. Appealing to the broad demographic diversity of the party is an absolute imperative for 2020. But presidential candidates should not conflate that with appealing to the far left with populist rhetoric and a democratic socialist agenda.

To sum up, the lesson from 2018 was that moderate Democrats could flip seats from red to blue. While they won over college-educated suburban voters, they also ginned up turnout among young and nonwhite voters. What exactly is the strategy then in finding the most extreme nominee for the 2020 Democratic presidential nomination? You got me, but that’s why President Trump goes out of his way to compliment Sen. Bernie Sanders (I-Vt.), who offers Trump the hope that the Democratic nominee will turn off moderate whites without necessarily supercharging nonwhite voters.

But, you say, look at Hillary Clinton. She was a moderate and didn’t turn out the base the way she needed to. (The Post observed that “the Obama-to-Trump voter pool was overwhelmingly white — and the Obama-to-nonvoting pool disproportionately black.”) The answer should be obvious: There are effective moderate candidates and less effective ones; there are moderates who can present a change agenda and those who sound as though they are defending the status quo.

Fast forward to 2019. We see former vice president Joe Biden leading strongly among moderates and nonwhite voters. That’s entirely consistent with the 2018 experience.

Nevertheless, six months after the midterms, the temptation to go far left remains despite the midterm experience. Presidential campaigns are still bamboozled by ultra-progressives goading them to take more radical positions. Despite all the available evidence, the media still insists that the party is being pulled to the left. Taking the left-wing bait would be foolish for presidential aspirants, and voters would be foolish to buy in to the “Democrats go far left” punditry. It’s essential for Democrats to resist the impulse to run to the left if they want to boot Trump out.

“White voters ... — including the well-educated ones moving away from Trump’s insular definition of the GOP — are flashing an unambiguous yellow warning light about Democrats’ most ambitious and expensive ideas to expand government’s reach,” writes Ron Brownstein. “If Democrats barrel through that signal in 2020, they will be wagering that they can beat Trump with a very different coalition— that relies more on enhanced minority and youth turnout — than the one they marshaled to recapture the House in November.”

And since we know that moderate Democrats can win with enhanced minority and youth turnout, it really makes no sense strategically to go far left. Moderates can deliver the best of all worlds — a broad coalition of suburban whites, minorities and young voters.

This does not mean that Biden is the inevitable nominee. Like any candidate, he has weaknesses; he gives up some advantages over Trump that other candidates would have (youth, outsider status). However, it should persuade Democratic candidates in the race vying to knock Biden out to hold their ground on the center-left. The data should also convince them that moderate ideology and diverse support correlate (whereas socialism and diverse support do not). Democratic primary voters desperate to win need not worry that the nonwhite and young members of the base won’t turn out for a moderate; they did in 2018, and they can again in 2020.

Read more:

Jim Kessler and Lanae Erickson: Don’t let progressives fool you. Moderate Democrats can win.

Joseph E. Stiglitz: A ‘democratic socialist’ agenda is appealing. No wonder Trump attacks it.

Jennifer Rubin: Voters aren’t playing along with the media narrative

Max Boot: Democrats need to beware their loony left