It’s dark inside Joe Biden’s campaign bus, a lumbering blue diesel emblazoned with the slogan Battle for the Soul of the Nation. On this late January afternoon in Iowa, the former Vice President is in the cramped back cabin, nursing a paper cup of Panera Bread coffee so the motion of the road and the drone of the motor don’t lull him to sleep.

He is talking about loss. The things he has lost are never far from Biden’s mind. Chief among them: his son Beau, a rising star in Democratic politics who died of brain cancer in 2015, a few months after his 46th birthday. “I get up in the morning lots of times and ask myself if he’d be proud of me,” Biden says.

Beau’s death was the latest in the litany of losses and setbacks that have defined Biden’s life. The death of his wife and daughter in an auto accident in 1972. The 1988 presidential bid that ended in a plagiarism scandal. Life-threatening brain aneurysms. Another failed bid for the presidency in 2008. For nearly a half-century, the nation has watched Biden wrestle publicly with sorrow. At countless funerals, he has eulogized Americans great and ordinary, all while nursing his own barely concealed wounds. “My mother used to say God never gives you a cross too heavy to carry,” his wife Jill says. “But God got pretty close with Beau.”

Yet Biden soldiers on: out of pride, out of duty, out of a deep-seated need to remain in the mix. To his boosters, he’s the last authentic man in American politics and the Democrats’ best hope of toppling Donald Trump. To his critics, he’s a nostalgia act whose well-worn slogans about middle-class uplift and national unity are out of sync in this season of outrage.

Biden on the campaign trail in Iowa, where his crowds have been smaller than those of his top rivals September Dawn Bottoms for TIME

Now, at 77, he stands atop the field of Democratic presidential contenders. For months, rivals have nipped at his heels, evincing an I-can’t-believe-I’m-losing-to-this guy incredulity. His campaign is disorganized, his debate performances uneven, his stump speech a long-winded hodgepodge delivered to small, graying crowds. Anyone who’s known him can see he’s slowed down. And yet, as the Feb. 3 Iowa caucuses draw near, Biden remains the man to beat for the nomination. He has maintained a lead in national polls since the start of the campaign, bolstered by a durable coalition of African American and white working-class voters drawn to his experience, his relationships and his humanity. No one in either party connects with voters in such an intensely personal way: hugging, gripping shoulders, planting kisses on foreheads. “He’s got more compassion in his little finger than anyone I’ve met,” says Mary Luce, a 70-year-old bartender at an American Legion post who lingered to speak with Biden after a town hall in Ottumwa, Iowa. “That’s what would make him such a good leader.”

The outcome of the Democratic primary and potentially the party’s fate in November hinge on Biden’s resilience and whether he can overcome one last test. Embedded in the challenge are existential questions about grief and experience: Do they add or detract? Are they baggage or scar tissue? Do they strengthen a person or deplete him? In Biden, both possibilities are simultaneously present.

Politics has always been a cathartic exercise for Biden, a form of exuberant self-expression. It’s as if he has to prove to himself he’s still alive, and this is the only way he knows. “Purpose,” he says. “That’s how I got through it. I lost my wife and daughter; that’s how I got through it. When they told me Beau didn’t have a chance of making it, that’s how I got through it. You’ve got to have purpose.”

This time is no different. Biden’s iPhone rests on the table in front of him, a platform bolted to the wall of the bus. The phone is open to a text-message conversation in enlarged type, the sender identified as “HUNT”: his younger son Hunter, the one with the soap-opera life and foreign entanglements that figure into President Trump’s impeachment. The only visible message reads, “Love you Dad.”

Biden, in Mason City, Iowa, on Jan. 22, connects with voters in an intensely personal way September Dawn Bottoms for TIME

The bus pulls onto the campus of Iowa Central Community College in Fort Dodge, a city of 24,000 an hour and a half north of Des Moines. The sun has set by the time Biden finally gets started, nearly two hours late. Despite the venue, the crowd is elderly. As Biden speaks, students drift out of the adjacent library without stopping to listen.

Something in the front row catches Biden’s eye, inspiring a riff about the three times firefighters saved him and his family members, starting with the car crash that killed his wife Neilia and 13-month-old daughter Naomi but spared his two young sons. It’s been less than three minutes and already we’re talking about the Jaws of Life. Then the story ends, and Biden, who’s pacing the room with a microphone, left hand tucked in the pocket of his slim navy suit, moseys back to his lectern, scanning his notes for a rhetorical foothold. “But look, folks, um, one of the things that, uh, that I think is pretty critical here is that, uh, you know, uh I think the character of the nation is literally on the ballot this time around.”

Biden spent his early years watching his father struggle in business. At one point the family had to live with his mother’s parents, a feuding, hard-drinking Irish clan. When Biden was 10, the family moved to Delaware, where his father worked as a car salesman. The Bidens never sank into poverty but were never comfortable either. Joe struggled to overcome a childhood stutter; his mother assured him it was because he was so smart his mouth couldn’t keep up with his brain.

During college at the University of Delaware, Biden worked as a lifeguard at a swimming pool in a rough, mostly African-American neighborhood in Wilmington. “You couldn’t run up on him and scare him,” says Richard “Mouse” Smith, who befriended Biden at the pool and remains close. “If you got in his face, he got in your face. He didn’t back down for nobody.”

The Bidens at their family home in the 1950s; Joe is second from the right Courtesy Biden Campaign

When Biden ran for Senate in 1972, people said he was crazy to take on the well-liked Republican incumbent, Cale Boggs. Biden responded, “He’s tired.” The 29-year-old wunderkind thrilled audiences with soaring oratory, each speech a feat of Kennedy-esque optimism that defied the Vietnam-era gloom. Smith helped introduce him in Wilmington’s housing projects, where white politicians rarely ventured. It was a bad year for Democrats, the year of President Nixon’s landslide re-election, but Biden won by a razor-thin 3,000-vote margin.

Just a few weeks later, while Biden was in Washington interviewing staff, a tractor-trailer slammed into the family station wagon. “One of the things that made it so excruciating is that it came right after something fantastic happened to him,” says Ted Kaufman, who was a 33-year-old volunteer on the ’72 campaign and would later become Biden’s chief of staff, close confidant and appointed successor in the Senate. “He won this impossible, come-from-behind race for the Senate seat at 29 years old. We were top of the world, and then we were down at the bottom.”

Biden’s sons Beau, then 3, and Hunter, 2, were badly injured. Once Biden got to the hospital in Wilmington, he refused to leave their side. He told the Senate majority leader, Mike Mansfield, that he wouldn’t return to Washington and sent word that the incoming governor of Delaware should prepare to appoint someone else. The tragedy plunged him into such despair, Biden wrote in his 2007 memoir, that he came to understand why those who commit suicide see it as a rational choice.

Mansfield arranged for Biden to take the oath of office at the hospital and wouldn’t leave him alone until he agreed to stay in the Senate. Biden never rented an apartment in Washington, commuting two hours each way by car or Amtrak so he could be home in Wilmington every night. The meaning he found in his work helped pull him through the tragedy’s aftermath; the Senate became a sort of second family.

Mourning his wife and daughter, Biden is sworn in at his sons’ hospital room in 1973 AP

Slowly, Biden put his life back together. In 1975, after a few years as a single father, he asked Jill Jacobs on a date after spotting her picture on an airport poster and discovering his brother knew the onetime model. “It wasn’t like Joe and I dated—I dated Joe and the boys,” Jill Biden says. “I watched him heal through his love for the boys.”

By 1987, Biden was chairman of the Judiciary Committee and running for the Democratic presidential nomination. His campaign was a high-wire act, a succession of late entrances and ad-libbed last-minute speeches. Instead of preparing for a debate at the Iowa State Fair, Biden spent the entire flight westward gabbing with aides about Senate business and failing to prepare a closing statement. He could talk forever, but he could never quite articulate why he was running.

Unable to come up with his own message, he substituted those of others. He claimed to have marched in the civil rights movement when he hadn’t, and he lifted passages from the late Bobby Kennedy’s speeches. Finally, in a debate, he recited nearly word for word, without credit, British Labour Party leader Neil Kinnock’s impassioned monologue about his coal-mining ancestors. Biden was not descended from any coal miners. A rival campaign tipped off the press. It was soon discovered that he’d also been disciplined for plagiarism in law school.

Biden’s political rhetoric had invoked the sacredness of a man’s word. The scandal cast him instead as a blarney artist, a man so in love with the power of a good story that facts were incidental. He withdrew from the race before voting began.

Biden’s first presidential campaign ends before any votes are cast, amid a plagiarism scandal in 1987 Getty Images

For the next 20 years, Biden worked to reclaim his reputation as a serious man. “It obviously jolted him,” says former Secretary of State John Kerry, a longtime Senate buddy who is now campaigning for Biden. The same day Biden pulled out of the presidential race, he returned to the Senate to question witnesses about President Reagan’s conservative Supreme Court nominee, Robert Bork. Biden won over six Republican Senators to derail Bork’s nomination on ideological grounds, a feat that broke the Senate’s norm at the time of evaluating judicial nominees only on the basis of aptitude.

A few months later, Biden fell ill in a hotel room after a speech. He underwent two high-risk brain surgeries to repair cranial aneurysms. Doctors told him he had no better than 50-50 odds of recovery. Biden was out of the Senate for seven months but recovered and went on to rack up a long record of accomplishments. He became chairman of the Foreign Relations Committee and won acclaim for his ability to work across the aisle. “I saw him negotiate with Jesse Helms to get funding for the U.N.,” recalls former Senator Chris Dodd. “No one else could do it.”

Today the deals Biden cut with Republican Senators, including segregationists like Helms, are part of the left’s case against him. Biden took the lead in passing the 1994 crime bill, which included a ban on assault weapons and the Violence Against Women Act but also increased criminal penalties that have been blamed for America’s mass-incarceration crisis. When he ran Clarence Thomas’ 1991 Supreme Court nomination hearing, he initially resisted airing Anita Hill’s allegations of sexual harassment, then presided over an all-white-male panel that treated Hill with skepticism and condescension.

After Anita Hill accuses Clarence Thomas of sexual harassment, Biden presides over an all-white-male panel in the Senate in 1991 Getty Images

Biden voted for welfare reform and banking deregulation, NAFTA and the war in Iraq. He clashed with a little-known professor named Elizabeth Warren over bankruptcy legislation that Warren said would leave the working class without a safety net. Biden, whose home state’s lax financial regulations have drawn many banks and credit-card companies to make their headquarters there, ushered the bill through. “Every big mistake Democrats have made in the past 30 years, Joe Biden has been involved, and often he’s been leading the way,” says Rebecca Katz, a progressive strategist unaffiliated with a presidential campaign.

Biden’s second presidential run, in 2008, was overshadowed by Barack Obama’s meteoric ascent and Hillary Clinton’s establishment machine. He dropped out after getting 1% in Iowa. But Obama had been impressed by Biden’s debate performances and wanted an elder statesman to balance the ticket. Biden agreed to be vetted for Vice President and was interviewed by Obama’s senior strategist David Axelrod. “I said, ‘One thing that concerns me is that you can be a little voluble. Can you control that?’” Axelrod recalls. “Two hours later, he finished answering the question.”

Obama and Biden were opposites in background and temperament, but they became genuinely close, according to both men. Biden commanded an expansive portfolio: implementing the Recovery Act and a gun-control push, handling sticky foreign situations from Iraq to Ukraine and doing much of the Senate glad-handing that Obama loathed. Biden also argued for a restrained foreign policy, frequently clashing with the more hawkish Secretary of State Clinton and Defense Secretary Robert Gates. Biden advised against the raid that killed Osama bin Laden and against sending more troops to Afghanistan.

Biden helps write the controversial crime bill signed by President Clinton in 1994 AP

Within the Administration he was a serious player, but he was also known for his antics. Upbeat and gregarious, he couldn’t walk down a hallway without pigeonholing someone for a 10-minute conversation, a former West Wing staffer recalls. He carved out a public persona as a sort of lovable goof, encapsulated by a parody in the Onion of a shirtless “Biden” supposedly washing his vintage Pontiac Trans Am in the White House driveway. His staff once blacked out the windows of a venue where he was speaking because his tendency to bound outside to shake hands presented a security risk and scheduling hassle.

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Obama aides mostly laughed off Biden’s idiosyncracies; they’d known what they were getting when they picked him. There was one notable exception. In May 2012, Biden let slip that he’d come around to supporting gay marriage, forcing Obama to announce ahead of schedule that his own position had also “evolved.” Obama’s advisers, some of whom had tested the idea of replacing Biden with Clinton on the 2012 ticket, were incensed. Today Biden invokes their partnership incessantly, but Obama remains officially neutral in the primary.

Some of Biden’s critics charged that he was so eager to be part of the action that he would agree to bad deals in the name of bipartisanship. In December 2012, then Senate majority leader Harry Reid and minority leader Mitch McConnell reached an impasse on an extension of the George W. Bush–era tax cuts. Reid was so annoyed with McConnell’s offer that he threw it in a fireplace. McConnell “called Biden because I didn’t want any part of that deal,” Reid recalls. “I was not a big fan of it, but it got done.” Reid later demanded the White House remove Biden from future negotiations.

Obama taps the senior Senator to join the Democratic ticket, and the Senator is elected Vice President in 2008 Getty Images

The morning after the speech in Fort Dodge, Biden arrives at the North Iowa Events Center in Mason City, where he’s introduced by Representative Conor Lamb of Pennsylvania, a 35-year-old who in 2018 won a district Trump had carried by 20 points. Youth and diversity are great, Lamb says. But “a little adult supervision wouldn’t be the worst thing for us in the House!” Taking the microphone, Biden extols Lamb’s credentials. “He reminds me so much—excuse me for saying this—of my son Beau,” Biden says. “They both ended up majors, they both ended up deployed, and they both ended up serving their country from their heart as well as their head.”

Beau was the attorney general of Delaware, laying the groundwork to run for governor, when in 2013 he was diagnosed with glioblastoma, the same fast-moving brain cancer that killed Senators John McCain and Edward Kennedy. “It’s a death sentence. We knew right away,” Biden recalls in our interview. “But you always hope for a miracle.” Beau succumbed to the disease in May 2015. Before he died, he made his father swear that he would be all right, as Biden describes in his best-selling 2017 memoir, Promise Me, Dad—a deeply moving chronicle of loss that’s interwoven with descriptions of Biden’s high-stakes negotiations with foreign leaders. At first, Biden wasn’t sure he could keep that promise. The boys had gotten him through his grief after the car accident, he says. Coming home every night “wasn’t about being a good dad—I needed them.” Now his support system was gone.

Biden had been making serious preparations to run for the 2016 presidential nomination, despite the conventional wisdom that Clinton had it locked up. His strategist Mike Donilon drew up a 22-page memo arguing that he was well positioned to win with a message of finishing the work Obama started and lifting up the middle class. Even Biden’s gaffes, he argued, would strike voters as authentic and refreshing compared with “carefully packaged candidates” the public had tired of. But Biden says, “I realized I just didn’t have the heart to do it.”

Beau’s death had destabilized the family in more ways than one. His widow fell into a romance with his brother Hunter, who had separated from his wife. Hunter had struggled with addiction for years—in 2014, he was discharged from the Navy when he tested positive for cocaine. He’d been to rehab, but after his brother’s death, he resumed drinking and smoking crack, he told the New Yorker last year. He recently settled a paternity suit brought by an Arkansas woman in local court. In May of last year, Hunter surprised his parents by suddenly marrying a South African filmmaker he’d met six days earlier. (Hunter Biden did not respond to messages requesting comment for this article.)

Biden and his family at a visitation for his son Beau in 2015 AP

Hunter’s career has also created issues. After graduating from Yale Law School, Hunter founded a series of lobbying and investment firms that Republican critics charge were mostly about leveraging his name. These activities caused heartburn in the White House, Obama Administration sources say, but Biden would become defensive or irate if anyone questioned them. One of his gigs was with the Ukrainian gas firm Burisma, which paid him up to $50,000 per month to sit on its board despite Hunter’s lack of expertise in Ukraine or natural gas. At the time, Joe Biden was leading anticorruption efforts in Ukraine, and from this potential conflict of interest, Trump and his allies have spun an elaborate and false conspiracy theory alleging that Burisma was bribing Joe Biden, through his son, to influence U.S. policy toward the former Soviet state.

After 2016, Biden’s political career was assumed to be over. But Biden still nursed ambitions. Trump’s “flat appeal to hatred” after the deadly white-supremacist protest in Charlottesville, Va., in August 2017 was a key factor, he says. Still, he wasn’t sure about running, “because I knew how ugly he’d make it.”

Biden’s 2020 campaign has been messy and insular, like all his previous ones. This is the first time his sister Valerie Biden Owens hasn’t managed the operation, though she’s still deeply involved. His senior leadership is heavy on confidants and light on consultants-for-hire, with few veterans of other presidential campaigns and few former Clinton staffers.

The candidate is prone to indecision, sometimes paralyzingly so. The campaign’s kickoff was delayed for months as he dithered. In April, aides planned to launch at last with a video, filmed in Scranton, Pa., about middle-class values. At the last minute, Biden ditched it and recorded an ad about Charlottesville instead. It took months for the campaign to open its Philadelphia headquarters. When the Ukraine scandal began to unfold in September, Biden initially struggled to respond to questions about his son’s role.

All of Biden’s top Democratic rivals routinely draw larger and more enthusiastic crowds. At events he is usually preceded onstage by a young field organizer, a tactic Obama’s team seized on to encourage volunteering. But on his recent campaign swing, all the field organizers were from out of state, a sign that he’s having trouble recruiting local volunteers.

Then there’s the candidate himself. Some days he seems lost; others, he’s perfectly sharp. The campaign has sharply limited his exposure to the media. Biden hasn’t taken questions from reporters on the campaign trail in more than a month. Aides cut off the interview for this article before the allotted time was up. “They’ve been very careful how they handle him,” Axelrod observes. “He’s like a porcelain candidate—they don’t expose him very much. I used to say Biden has a peculiar type of performance anxiety: he performs, and everyone around him is anxious.”

The old Biden gaffes tended to be a product of political incorrectness, like when he called Obama “the first sort of mainstream African American who is articulate and bright and clean and a nice-looking guy.” Now Biden often wanders around searching for the end of his sentence, cutting off digressions with an apologetic “anyway.” The fast-talking, wisecracking lawyer-pol has been replaced by an old man who can’t stop talking about the past.

Biden waits backstage before his campaign event in Mason City September Dawn Bottoms for TIME

And yet when Biden gets into the weeds on policy, a sort of muscle memory kicks in. He ticks off the legislative history of bills and makes sophisticated arguments and has a remarkable ability to weave together his aw-shucks persona with his high-level experience. One minute he’s cracking jokes about firefighters (“You’re all crazy, but I love you”), and the next he’s recounting his meetings with Chinese President Xi Jinping. The New York Times editorial board gave him scant consideration for its endorsement but noted he was the only candidate they interviewed who offered a detailed plan for what to do if China sent troops to quell the Hong Kong protests. (U.N. resolution, warships moved to the region, pressure from allies, threats of sanctions.)

The most telling moment from Biden’s session at the Times came not in the interview but beforehand, when an African-American security guard approached him in an elevator to tell him she loved him. In the 2020 campaign, this has been Biden’s abiding strength: the loyalty of voters who feel they know him deeply. “He has a real base among African Americans, non-college-educated whites and older voters,” Axelrod says. “He has a palpable sense of empathy and compassion, and when the race is defined by a President who’s completely devoid of empathy and compassion, that is a powerful quality.”

Almost anyone who knows Biden can offer a story about this compassion. Representative Lisa Blunt Rochester, a Delaware Democrat, was not yet an elected official when her husband died unexpectedly in 2014. Biden tracked her down and called out of the blue to comfort her. “I got a lot of calls that day. I don’t remember a lot. I was in a fog,” she says. “But I’ll never forget the conversation with him. Through the phone I could feel true empathy from somebody who had walked that path.” She only found out later that Biden’s son had a terminal illness at the time.

Biden’s events can feel like a rolling therapy session. A large chunk of time is set aside after every speech for Biden to interact with voters, many of whom tell him about their own encounters with trauma and death. Most people would find this constant performance of comfort, the assumption of so many strangers’ burdens, to be draining. Not Biden. “Joe’s a healer,” Jill says. “He feels people’s problems because he’s been through a lot of it himself. And it satisfies that feeling of purpose that he’s helping others.”

Biden’s most consequential decision this campaign has been not to make a hard turn to the left. (Some of his advisers pushed him to reconsider defending his work on the crime bill. He refused, saying it demonstrated his pragmatism.) Pressed to apologize for working with segregationists in the Senate, he insisted it proves he can work even with today’s Republicans. “Some of my colleagues don’t think we can unite the country,” Biden says on the bus, positioning a throw pillow at the small of his back on the narrow bench. His jacket is off, his tie loosened. “They make fun of me that I think I can,” he continues. “Well, if we don’t unite the country, if we don’t bring it back together, start to be able to work together, we’re done.”

It’s a gamble to hawk comity while your rivals inveigh against a broken system and a bitter enemy. Taking in Biden’s long-winded Q. and A.s can feel like a warm bath: not necessarily thrilling, but deeply soothing. His advisers believe voters are hungry for reconciliation. “They’re scared to death because they think the character of the country is going to change in a way that will never be repaired,” Donilon, the campaign’s chief strategist, says of voters. “That’s what Biden is talking about. That is a resilient message.”

The other key pitch is that Biden offers the best chance of beating Trump. “We can win in North Carolina, we can win in Georgia, we can win in Texas, we can win in Arizona, we can win Pennsylvania,” Biden says. “The question is, who do you think helps? You think Bernie or Elizabeth helps them win in North Carolina or Georgia? You know the answer.”

Yet many Democrats fear nominating Biden is a disaster waiting to happen. Trump could run the same playbook he ran against Clinton: insinuating physical decline, pointing out paid speeches and other ties to big banks, the vague scent of legal-but-sleazy associations, “experience” turned into an epithet against the longtime Washington insider. Biden allies recognize the threat and insist they’re girding for a brawl. Says Senator Chris Coons of Delaware: “We’re going to go right back at him.”

Biden’s bus trundles on through Iowa, the windows so darkened by his campaign slogan that it’s impossible to see the landscape as it passes by. “My mom used to say, as long as you’re alive—” he pauses and emits a chuckle. “You’re not dead until you see the face of God.” —With reporting by Philip Elliott/Des Moines, Iowa

Write to Molly Ball at molly.ball@time.com.