Since President Donald Trump took office, Democrats have been having a passionate debate about what matters more: increasing progressive turnout or winning over swing voters. And there is no doubt that both tactics help Democrats win elections. But the evidence about which tactic matters more is pretty overwhelming. Persuasion does.

Take one stark pattern: In the 2018 midterms, many Democratic candidates who ran persuasion campaigns flipped areas that had gone for Trump in 2016. Not a single Democrat won a competitive state or House district with an unabashedly progressive campaign.

Yet the presidential field is dominated by candidates who haven’t had to worry about persuading swing voters in years, if ever. Delaware (Joe Biden’s home), Massachusetts (Elizabeth Warren’s) and Vermont (Bernie Sanders’) all voted against Trump by large margins. Pete Buttigieg and Mike Bloomberg were each the mayor of an overwhelmingly Democratic city.

The best case for Amy Klobuchar is that she’s the only remaining candidate with a track record of winning over the kind of voters that the Democrats will need to beat Trump. She has built her career on a middle-class image that avoids the leftism of Sanders or Warren and the elitism of Buttigieg or Bloomberg. As for Biden, Klobuchar looks sharper than he does — and she has a much more impressive electoral history.

She won all three of her Senate campaigns in Minnesota by more than 20 percentage points. Trump, by comparison, lost the state by only 1.5 points in 2016. Klobuchar did it by winning suburbs that normally lean right and holding her own in many rural areas.

Her strategy isn’t exactly a secret. It is the same one that many congressional Democrats used in 2018, and not so different from Barack Obama’s approach to his 2012 re-election. She emphasizes the pocketbook issues on which Democrats hold a huge advantage over Republicans. She doesn’t make voters anxious by promising utopian dreams, like a mandatory version of Medicare that would ban private insurance. She promises to reduce the cost of medical care — and points out that Republicans will raise those costs.

Klobuchar also finds ways to demonstrate her respect to voters who disagree with her on many issues. She describes Minnesota as “a proud hunting state” and visits each of its 87 counties every year. She doesn’t take unpopular positions on immigration, like border decriminalization.

And yet Klobuchar is hardly a centrist. She wants to raise taxes on the rich, break up monopolies, vastly expand Medicare, fight climate change, admit more refugees, allow immigrants in the country illegally to become citizens, ban assault weapons and require universal background checks. A Klobuchar administration would probably be well to the left of the Obama administration.

Mike Pence, Trump’s vice president, has long said that he is conservative but not angry about it. Klobuchar is progressive without being angry about it. The combination can allow a politician to win the middle without being of that middle.

At this stage, of course, Klobuchar is unlikely to be the nominee. She hasn’t quite figured out how to adapt her approach for the scale of a presidential race. Too often, she still seems to be running for Senate, talking about committee assignments and legislative co-sponsors instead of telling a story about the country.

Still, Democrats would be wise to remember that her success in Minnesota is no mystery. It is the main way Democrats have won elections over the past decade, and it’s a strategy that any Democratic nominee, even Sanders, can mimic:

Pound away at simple economic issues — on which the country’s voters are legitimately progressive. De-emphasize cultural issues — on which voters are much more divided. And don’t give in to fantasies involving millions of left-wing nonvoters who are just waiting to show up at the polls.