People won Mr. Obama’s campaigns. From the black beauticians in South Carolina to the white and black retirees in Pennsylvania to the Latinx supporters in Nevad a, hundreds of thousands of volunteers knocked on doors and made calls from the primaries through the general elections. And Barack Obama saw them, spoke to them and loved them.

As the primary campaign heated up in 2007, my colleague Jeremy Bird and I trained and coached organizers in South Carolina to tell their own family stories and to identify community leaders by askin g the m to host meetings in their homes with their friends and family, to build and train volunteer leadership teams and to equip those teams to make strategic decisions about how to engage voters in their neighborhoods.

The strategy soon paid off. After an incredible win in the Iowa caucuses, the campaign lost in New Hampshire and Nevada. But on Jan. 26, 2008, the volunteers of South Carolina, who had organized block by block to cover the entire state, delivered the primary to Barack Obama with a 29 percent margin over the runner-up, Hillary Clinton, breathing oxygen into the campaign for the months ahead.

We replicated this experience in Pennsylvania. We registered more than 100,000 new voters in just over a month, shifting the electorate there and organizing an animated base that would deliver the state for Mr. Obama in the general election.

Then in the spring of 2008, the campaign leaders took an extraordinary risk. They allowed a few top organizers to hunker down in Chicago to design a field program that required paid staff to organize our base over the summer — predominantly black and young volunteer activists, as well as white and Latinx people who were proud to support a black candidate.

We decided to empower and animate our most excited supporters, rather than working around them, or even worse, betraying them in pursuit of the elusive white swing voter. Most other campaigns would have gone straight to paying staff members to knock on unfamiliar doors and make cold calls.

And we won.

So I was surprised when, after the election, I came bright-eyed into a project where I interviewed senior Democratic consultants to help train campaign managers for the midterms. Here’s wh at they told me: We’re going to have an extraordinary backlash to President Obama’s victories, so we have to double down on likely white voters. After two cycles of terrible midterm losses, this was, again, the narrative after the 2014 elections.