Door knocking is tough these days. Harris' team is betting on apps.

Milwaukee: Clutching a fistful of Harris campaign pamphlets, George Pumphrey Jr hunched in front of a doorbell camera in a neighborhood in North Milwaukee and began yelling into the little digital peephole.

"I'm a volunteer!" he called out, asking to talk to the human inside the home, who was visible from the window but was busy watching television. A woman's tinny voice came through the peephole, asking Pumphrey to leave a few pamphlets at the door.

All in a day's unpaid work for Pumphrey, 75, who knocked on doors until his knuckles bled when Barack Obama was running for president in 2008. But now, he said, a combination of exhaustion, misinformation and wariness about strangers has made it harder to reach people in Sherman Park, the predominantly Black neighborhood where he spent some of his childhood.

"The only way to do this is to meet them face to face," he said as he walked down the street to the next house on his list. "But with all the craziness that's going on, people don't want to do that."

Pumphrey's experience does not signal the death of the door knock, exactly, but the reinvention of it, especially in places where would-be voters can be hard to reach.

In Milwaukee County, which is home to two-thirds of the Black residents in battleground Wisconsin, Vice President Kamala Harris' campaign is dispatching fleets of volunteers and relying on data-capturing apps to supplement the traditional work of door-to-door canvassing.

Technology might be making it easier to avoid a door knocker, but the Harris campaign is betting it can also help prompt voters to the polls on Election Day.

A few miles away from Pumphrey's turf in Sherman Park, a Harris campaign organizer and a volunteer were preparing to walk through the crowd at a youth football game to ask residents about how they planned to vote, and if they might be interested in volunteering.

The organizer, a 23-year-old named Star Walker who moved to Wisconsin from her native Texas to help turn out the vote among Black residents in Milwaukee County, helped a volunteer load an app called Reach into his phone.

When President Joe Biden was still in the race and the campaign belonged to him, officials tested the app in Milwaukee as a way to try to reach people who are harder to engage with during election seasons. These types of people might move around, changing addresses or phone numbers, or might be less inclined to respond to text messages and mailings.

Of more than 7,000 users in Wisconsin who have downloaded the app, about a third live in Milwaukee County. More than half of those users have signed up since Harris began her campaign in July, according to figures shared by the campaign. For every user who signs up, the app can map the person's social networks, supply Harris-specific content, and prompt more people to volunteer. Campaign officials say they have reached 38,000 voters in Milwaukee County this way, and the Reach app is now accessible across every battleground state.

Reach allows voters who have joined the app to mine their social networks for people who could be persuaded to support Democratic candidates, survey them on their political leanings and ultimately supply that data to the campaign. (Officials call this "friend banking," the idea being that campaign data harvesting is a little less annoying if it is done by friends and loved ones, preferably at an organized event like bingo or a happy hour.)

Paid organizers are more efficient.

At the football game last Saturday afternoon, one of Walker's first targets was a woman named Phebe McToy, a 34-year-old beauty adviser. At first, she waved Walker away with an assurance that she planned to vote for Harris, but she allowed her name to be plugged into the app anyway.

The app pulled up McToy's name and information, collected through voter file data purchased by the campaign, and offered an answer.

"This actually says you're persuadable," Walker said helpfully, reading from her phone. She spent several more minutes with McToy talking about her thoughts about Harris.

She ultimately declined to volunteer, but Walker, and the app, had captured enough information in that interaction to allow more volunteers to follow up with McToy closer to Election Day. The objective is to make sure that voters like McToy have a plan to vote and that their ballots will be going to Harris, campaign officials said.

Elsewhere on the field, Tierra Drake, 40, gave her information to Walker but said there was little Harris could do to persuade her to vote: "We've heard it all before," said Drake, a child care director. She said that she would vote for former President Donald Trump if she heard more from him about his economic policy plans, and about any policies he could offer that would provide better education options for her children.

"He does what he says he's going to do," Drake said. "Which is scary for what he's trying to do now, but you, know, that's the main thing."

Her information, too, was captured by the campaign and logged.

This person-by-person approach reflects a campaign that officials have long believed will be decided by the slimmest of margins. David Plouffe, a senior adviser to Harris, told New York magazine this week that he thought the race would probably fall within "a point, point and a half" in each of the battleground states.

"I think folks should focus less on, Why is it close?" he said. "It's going to be close. The question is, how do we eke out a very narrow win in enough places?" He went on, "You're fighting over a small number of voters in a small number of states, and you're fighting to win the turnout battle."

The data-heavy approach adopted by the Harris campaign is outpacing the Trump campaign's ground game across the battlegrounds, which relies more heavily on traditional canvassing to reach people. In a state like Wisconsin, which Trump carried in 2016 but Biden won in 2020 by 20,600 votes -- a total bolstered by Milwaukee County -- Trump campaign officials are betting that door knocking and a large mailing campaign can help reach people across the state's 71 counties.

Officials with the Trump campaign said that its efforts in Milwaukee had included opening an office dedicated to Black voter outreach and relying on volunteers for traditional voter canvassing. Two officials, who spoke on the condition of anonymity to discuss plans, said that the campaign was targeting messaging through platforms like TikTok on issues relevant to local voters, including the economy and school choice.

The campaign also unveiled Trump Force 47, an online tool that officials say has recruited thousands of people who have signed up to undergo training sessions to become "captains." Those volunteers are then presented with a list of 25 people the campaign has identified as persuadable voters. Their job is to talk to them about Trump and his policies. The campaign did not supply data about how many prospective voters had been reached this way.

Back in Sherman Park, Pumphrey ended his door-knocking session on Saturday after reaching only a handful of the homes that were on his list. Over the course of several hours, no Trump canvassers were spotted, but several other volunteers drifted from house to house across the street: "They're on my turf!" Pumphrey exclaimed at one point.

As his knocking continued, he spoke for several minutes to a resident who talked about government officials controlling the weather. On another block, a woman told him that her religious views had prompted her to disengage with politics, but that at her mother's urging, she planned to support Harris.

Outside a majority of the homes, though, Pumphrey pecked his notes into a canvassing app called Minivan -- "not home, not home, not home."

The app quietly stored the addresses as homes that other volunteers would have to try again later.