SOMEWHERE ON U.S. HWY 63, Iowa — Senator Cory Booker sat in the front seat of an S.U.V. grinning and, clutching his iPhone 11 Pro as he quickly took stock of the past 36 hours in Iowa.
It had been less than two days since Senator Kamala Harris announced she was leaving the 2020 race. Mr. Booker said it was “a problem” for the party and that it “hurt” him personally. It also gave him unexpected momentum for a four-day swing across Iowa; a last stand turned into a silver lining tour. He brought in $1.35 million in record time for him, earned new endorsements and drew overflow crowds.
Then his phone rang.
“I have a feeling that this is the downer part of the trip where you’re going to tell me that I need four polls and I’ve only got three polls left,” Mr. Booker said, with Matt Klapper, his senior adviser leaning in from the back seat. On the other end of the line, on speaker phone, was McKenzie Young, the opinion polling director.
“Oh no, we’re not there yet,” Ms. Young replied. “But I will say that there is just so much uncertainty that it is hard to say, and there’s not a ton of time left.”
For much of the call, the three focused on the unknowable (how many polls may be yet to come) and the likely outcome (not enough to get him on the debate stage).
Weeks ago Mr. Booker said that not making the December debate would force “difficult decisions” about his viability and his underdog candidacy. That was then. Now, things are looking a little bit different.
A speech in Des Moines on Thursday in which the senator from New Jersey decried a primary process that, at the time, appeared to leave an all-white field of candidates on the debate stage left Mr. Booker as the face of a reckoning within the Democratic Party over how the Democratic National Committee had set debate requirements.
Members of the Congressional Black Caucus were calling more frequently. Unexpected endorsements in Iowa rolled in, and major party figures who didn’t endorse were directing donations to his campaign, which raised a record $3 million in 18 days.
Of course, it is all relative: His fund-raising lags behind the current top tier of candidates. His overflow crowds that hovered between 100 and 150 were dwarfed by the more than 1,000 that showed up for Mayor Pete Buttigieg of South Bend, Ind. And in national polling, he remains stuck at around 2 percent, which will likely keep him from the debate stage.
The criticism that has dogged his campaign from the start — that he has all the qualifications but doesn’t have that killer instinct to break through — hasn’t led to any strategic shift. He still wants to “lead with love,” not hit his opponents.
But with the energy the candidate said he was feeling on the ground, he was ready to call for a surprise in Iowa.
“If we show that in this crowded field, we could come out in the top three or four, and beat people who are the presumptive front-runners right now,” Mr. Booker said in an interview, “that will really be the starting moment of the campaign to show who the true front-runners are.”
So, in need of a moment — though Mr. Booker might not want to say it — was it good for him that Ms. Harris, the California senator, called it quits?
“The turning point is definitely not Kamala deciding to drop out, which has certainly helped,” Mr. Booker said. “She and I had a lot of synergies in this race, and I had people tell me all the time they were torn between the two of us. So we know that that is giving us more momentum, but clearly something happened in that last debate that really propelled us forward.”
Indeed, it propelled him right to a crowded Iowa City basement, an Iowa Farmers Union forum, a meeting with the Teamsters and a weekend of events in 12 of Iowa’s 99 counties.
This is what 48-hours inside a sudden turnaround looks like: Welcome twists mixed with heartfelt phone calls, a stump speech that brings audiences to tears, a town hall routine full of hugs and dad jokes, powered by a lone S.U.V. stacked with vegan goodies and a candidate who is genuinely having the time of his life.
“Dan, it’s Cory, I’m driving through Iowa cornfields man, what could be better?” Mr. Booker said on the phone with a donor Thursday afternoon, calling from the back seat of his S.U.V. en route from Des Moines to Council Bluffs. The person on the other end of the line is a “clutch player,” Mr. Booker said. “I know you’re still hustling. But thank you for all you do.”
The call dropped.
“Frose, damn it man!” Mr. Booker jokingly said to his Iowa state director, Mike Frosolone, pointing to the one bar of service on his phone. “I was having the conversation that was going to transform the campaign.”
“Well, we need some serious infrastructure investment,” Mr. Frosolone said, “which is why we’re going to brief your rural agriculture plan in six minutes.”
By 9:30 p.m. on Thursday, Mr. Booker was still pulling in donors. A man from Louisiana named Skeeter called to say that he and his wife would be making the maximum donation of $2,800. The candidate turned around from the front seat with a pumped fist.
In interviews with six longtime donors to Mr. Booker, two expressed skepticism about his prospects, saying this “just may not be his year.” The others pointed to Ms. Harris’s exit as a moment. But all pledged to continue supporting him financially.
“A lot of people have been with Cory and have been supporting him for two decades, and he’s only 50 years old,” said Whitney Tilson, a longtime fan who said Mr. Booker “would surprise everybody” in Iowa because of his high favorability ratings — people who like him but aren’t committed to caucusing for him — in the polls. “He will be president someday.”
At 7:30 p.m. on Friday, on the way to his final event of the day, a fund-raising call with Judy Zamore, his campaign’s chief financial officer, and Addisu Demissie, the campaign manager, revealed the weeklong surge.
“We are about $1,000 shy of having $1.1 million in for the week, that’s pretty amazing for us,” she said. But Ms. Zamore warned that “it is definitely starting to come back to earth a little bit,” and the possibility of missing the debate stage could make it much harder to continue at the current pace.
One key to the Booker campaign’s relative staying power is an extreme dedication to frugality, set by Mr. Demissie and Ms. Zamore. They have staff make their ads in house, instead of hiring an outside consultant. On the road, Mr. Booker regularly stays in supporters’ homes, and has staff do the same. At every all-staff meeting, Mr. Demissie gives out “super saver awards” to especially budget-minded staffers, like those who car-pooled instead of taking a train.
But a tight budget has also significantly hampered the operation. The campaign has still not advertised on television, and only this week began running digital video ads. And while they have a broad staff of organizers on the ground, the campaign has only five field offices in Iowa. As of October, Mr. Buttigieg had 22 field offices across the state.
Though Ms. Young, the pollster, had explained to Mr. Booker that time was running out for him to meet the polling thresholds for the December debate, the candidate was still exploring his options.
He asked if polls currently in the field would change or recanvass after Ms. Harris and Gov. Steve Bullock of Montana dropped out. Ms. Young said it depended.
“That’s frustrating because Harris or Bullock people could very easily go to us,” he said.
Absent a likely polling boost, Mr. Booker turned to courting endorsements. His 84 endorsers in Iowa rank third, behind Mr. Buttigieg and Senator Elizabeth Warren of Massachusetts, according to the Iowa Starting Line tracker. His overall endorsements are also third in the race, according to FiveThirtyEight.
But in the wake of Ms. Harris’s exit, Mr. Booker had to strike a delicate balance. Cautious of moving too quickly or being disrespectful, Mr. Booker called two members of the Congressional Black Caucus, speaking in reserved tones and mostly echoing frustrations.
“Its been a rough week, I’m sure you’ve had the same experience I’ve had about just getting lines of calls of people who are just frustrated by Kamala’s exit,” he said in one call. “You know you have me in your corner.”
Late on Friday, Ms. Harris herself returned his call.
“I wish you could have heard pretty much all the conversations we had,” Mr. Booker told Ms. Harris, describing the “genuine love” he was still hearing from voters in Iowa about her. He said he wanted to visit over the holidays, which he was planning to spend in California with Rosario Dawson, his girlfriend. He promised to talk again soon.
A Buzz Simmers in Iowa
“Can I just make a comment?” Mr. Booker asked as he piled into the S.U.V. at 11:30 a.m. Saturday, flashing a smile at Ms. Dawson, who had just joined the trip, in the back seat. “I’m really feeling this energy right now.”
It was pretty clear that the debate stage would be out of reach, but Mr. Booker felt like he was on a roll.
In Iowa City, more than 100 voters mingled in an overcrowded basement, eager for selfies with Mr. Booker or Ms. Dawson.
Royceann Porter, the first black woman elected to the supervisor board of Johnson County and a sought-after backer, decided on the spot to support Mr. Booker, grabbing his hand and shouting her endorsement into the room, catching everyone by surprise.
Two mental health advocates in Iowa, Leslie and Scott Carpenter, also endorsed Mr. Booker, and brought him a tin of vegan snickerdoodle cookies.
And the candidate had just raised $2,000 for the Center for Worker Justice of Eastern Iowa through an impromptu $1,000 donation during his stump speech, which he said was only happening if 30 audience members also pledged to contribute what they could.
“At the end, when he talks about love all the time, and I try to talk about love in our community, it’s just, we have to work together,” Ms. Porter said.
She said she hoped that Mr. Booker was getting a new look after Ms. Harris left. “That is my hope, that the people who was for Kamala will come on board and support Cory. That is my hope. I really don’t know, but I’m hoping that’s what will happen.”
After each event, Mr. Frosolone and Tess Seger, the Iowa communications director, marveled at the percentage of attendees who signed cards saying they would commit to caucus for Mr. Booker. Conversion rates got as high as 40 percent. But in crowds of roughly 100, even a great conversion of 20 percent of attendees still only meant 20 people.
Throughout the weekend, former staffers for Ms. Harris in Iowa came to Mr. Booker’s events, with some now volunteering and others simply watching. In Davenport on Saturday night, three organizers — Matt Urquijo, Curtis Edmonds and Caroline Herriman — watched Mr. Booker’s town hall and hung around afterward to get a selfie and a hug from the senator.
All three had donated to Mr. Booker in the wake of Ms. Harris’s exit, as well as to Julián Castro, the former housing secretary.
But they were still unsure of what they would do next, professionally.
“I think the hardest thing for me is deciding should I jump on a candidate that I know can win,” Mr. Edmonds said. “Or should I jump on a candidate whose campaign shares the same values I do.”