MILWAUKEE — An energized crowd of 500 packed into a mixed-use space here on a summer Sunday afternoon to hear a rousing stump speech from Senator Cory Booker of New Jersey, who was making the final stop in a 12-day campaign blitz in a state that won’t hold its primary until April.
“A Democratic victory flows through cities like this,” Mr. Booker said afterward, noting that if voter turnout in Milwaukee, a heavily Democratic city where 40 percent of residents are black, had been as high in 2016 as it was for former President Barack Obama’s two elections, Wisconsin would have remained blue.
Seeking fresh energy for a presidential campaign that has lagged in the polls despite well-received performances in the debates, Mr. Booker was the latest candidate to detour from the conventional quartet of early-voting states to hold rallies in Detroit, Philadelphia and now Milwaukee, three cities where outsize turnout will be key to Democrats winning back Michigan, Pennsylvania and Wisconsin next November.
Mr. Booker’s plea to voters here was both personal and immediate, a primary pitch that he is the best candidate to re-energize the fractured Obama coalition and restore the black vote in key states Hillary Clinton lost by focusing on big cities that saw a drop in turnout. He argues that the path to defeating President Trump must involve black voters in these cities, and that Democrats cannot simply focus on disaffected white voters elsewhere.
“I’m the only candidate in this race who lives in a low-income, black and brown community,” Mr. Booker told the crowd here, a response he regularly gives when asked what sets him apart in the vast field of two dozen candidates.
“I see our country right now with so many places like Newark, like Milwaukee, like Chicago, like Baltimore,” he said. “There is something going on in our country right now where we are failing to have the necessary courageous empathy, where we see each other.”
The repeated and direct attention to swing-state cities at this early stage in the primary reflects a growing urgency to address the failures of the 2016 Democratic campaign, as well as the belief that Mr. Trump could win again if the party focuses on appealing to white, blue-collar swing voters in the Rust Belt, and makes less frequent overtures to core constituencies like people of color and young people.
“Three years ago, we didn’t show up to vote,” said Mandela Barnes, the lieutenant governor of Wisconsin and a Milwaukee native, as he introduced Mr. Booker on Sunday. “And it’s not that Donald Trump was some super-popular candidate. He got 6,000 fewer votes than Mitt Romney. We just have to show up.”
A national effort already underway
Evidence of the growing and focused effort on increasing turnout in cities like Milwaukee is abundant.
Priorities USA, a major Democratic super PAC, has launched an aggressive digital ad campaign in Michigan, Pennsylvania, Wisconsin and Florida, attacking the economic policies of the Trump administration. The group plans to spend $250,000 to $400,000 per week by late August.
The group is also spending $4 million to mobilize voters for the 2019 off-year elections. Though the group hasn’t detailed how that money will be distributed, many cities, including Philadelphia, are holding mayoral elections this year.
And for the past eight weeks, the Democratic National Committee has been training a group of college juniors, mostly from communities of color, to eventually work on the 2020 campaign, work-shopping best practices for door-knocking, phone-banking and recruiting.
In Michigan, the program, known as Organizing Corps 2020, had 45 organizers on the ground in the Detroit area this summer. They focused on proactive outreach, informing residents of recent changes to voting procedures, like the start of same-day voter registration and expanded access to absentee voting.
Here in Wisconsin, Jadah Cunningham, a rising senior at Indiana University-Purdue University Indianapolis, was one of 30 Organizing Corps members who canvassed every ward in Milwaukee, knocking on more than 20,000 doors, with a mandate to “bridge-build” while learning the ropes of the grunt work of field organizing.
“I think that that’s part of why Organizing Corps in Milwaukee exists in the first place,” Ms. Cunningham said. “The margins that we can win or lose by in 2020 are field margins, or margins that we, the 30 of us this summer, could potentially make up.”
Though the 2020 election may still feel far off, the goal of the Organizing Corps is to build an early bench of young people of color who are prepared to work in their own communities as organizers and field staff.
Central to the training effort this summer was combating voter suppression in cities. In his stump speech, Mr. Booker frequently references the 2018 governor’s race in Georgia, where Stacey Abrams, the Democratic nominee, was narrowly defeated amid accusations of voter suppression, particularly in black communities.
Though Mr. Booker boasted during the July debate that he was the only candidate talking about the suppression of black voters, the broader Democratic coalition is currently fighting to expand the electorate on both legal and organizing grounds.
The Priorities USA Foundation, a nonprofit group that is separate from the super PAC, is currently involved in voting rights litigation in Iowa, Missouri, New Hampshire and Florida.
The D.N.C. has already created a voter suppression hotline and an online resource guide, and the Organizing Corps has been reaching out in communities that were inundated with misinformation during the last presidential campaign.
Here in Milwaukee, that means focusing heavily on areas like the 53206 ZIP code, in which 95 percent of residents are black and the majority of men have been incarcerated.
“In the rest of the country, there’s a Democratic primary going on,” said Ben Wikler, the chairman of the state Democratic Party. “In Wisconsin, we’re already starting the general election.”
The state party in Michigan has created a dedicated, full-time position of voting rights director whose sole job will be taking a proactive approach to protecting voting rights in the state, such as tracking any purges of voter rolls.
Ask any expert whether Democrats can rely solely on these cities, however, and the answer is often a resounding “no.”
Priorities USA gamed out two general-election scenarios last month. In one, if the overall turnout from people of color drops two percentage points from current national poll numbers, the Democratic nominee will most likely lose the election. In the other, if support for the Democrat among white working-class voters drops one percentage point below current polling averages, the Democrat will also probably lose.
“It really is trying to find the sweet spot,” said Patrick Murray, the director of polling at Monmouth University. “The debate so far has been really focused on winning back that white, blue-collar, working-class vote. But it’s right to get your urban vote excited about you as well.”
An increasingly common campaign swing
Many of the Democratic candidates are making similar deviations from the state fairs, county dinners and fish fries of Iowa, New Hampshire, Nevada and South Carolina — the four states that are first to vote.
Senator Bernie Sanders dipped into a coffee shop meet-and-greet in Milwaukee, and Senator Elizabeth Warren campaigned there after unveiling her immigration platform. Senator Kamala Harris has made multiple trips to Detroit. Former Vice President Joseph R. Biden Jr. anchored his campaign in Philadelphia.
And national Democrats continue to telegraph the importance of these cities with major events: The July debates were held in Detroit; next summer’s convention will be in Milwaukee.
At the Booker rally, voters were relieved to see the growing attention paid to these cities amid a primary in which the four early-voting states always carry outsize import.
In Milwaukee, “it’s the same problem with what’s going on in the U.S.A. right now,” said Steve Morehead, 42, a lifelong resident. He said he believed cities like his hometown were being left behind.
Mr. Booker was the first candidate Mr. Morehead had seen in person this cycle, but he said he hadn’t yet decided whom to support.
Set against the national debate over gun control following the mass shootings in Dayton, Ohio, and El Paso, Mr. Booker spoke at length about the scourge of gun violence and its outsize impact on places like Milwaukee, drawing on similar themes as he did in a speech last week in Charleston, S.C.
“We pledge to be a nation of liberty and justice for all, but where is the justice when children are being killed every single day in our nation by gun violence?” he said.
He held his event in Sherman Park, the northern Milwaukee neighborhood where three years ago, a police officer shot and killed Sylville K. Smith, a young black man. The killing set off three days of unrest, with multiple arrests and injuries.
As he closed, Mr. Booker returned to his lofty and familiar themes of unity. The political and racial divisions stoked by the Trump administration, and often by the president himself, have left the country in need of more than just new leadership, Mr. Booker said. It needs to heal.
“I’m with you on beating him,” Mr. Booker told the crowd here. “But dear God, can’t we have bigger ambitions than that?”