I’ve known and covered Joe Biden since 1987 and written many stories about him. He appears at length in my book about American politics. In the fall of 2018, he came to lecture in the seminar I was teaching at the University of Pennsylvania.

“You’re in the Ivy League,” he told the students. “You’re smart; you’re going to do well. But, folks, there is no amount of money you can make – no wall you can build high enough – to protect yourself from changes in society. You have to get involved and be part of that change for the better.”

He charmed the kids, of course, and stayed to sign copies of his own book for each one. Afterwards, we chatted outside the classroom. Several things were apparent. One was how he looked. He was trim and wiry as always, but his skin was pale, almost translucent, and his eyes had faded to a lighter shade of sky. Over the decades, he’d had the gift of seeming younger than his age. No more.

The second: his still-burning ambition, powered, in part, by resentment at what he regarded as the way snooty people had underestimated him over the years. He was Delaware and Syracuse, not Harvard and Yale – or Penn. It bothered him. When I complimented him on his teaching, he reminded me that he had taught law school. When I told him he had framed the media and constitutional issues well, he told me that he had designed complex courses in law and policy.

The third: He refused to accept as final the judgment of fate that had burdened him with bad, even catastrophic, fortune over the decades. He had lost a wife and two children, embarrassed himself in two earlier presidential campaigns and, in his view, had been left to molder by Barack Obama’s decision in 2016 to back Hillary Clinton for the Democratic nomination.

“That was it for me,” he said. “There was nothing I could do.” Had things gone otherwise, in Biden’s view, he would have beaten Donald Trump in 2016. Looking ahead to 2020, he believed he was actually going to do it. It finally was his time.

It certainly appeared that way Tuesday night after he swept to crucial primary victories in Michigan and Missouri (and added two more in Idaho and Mississippi). Timing and context are everything in politics. Suddenly, all that bad kismet had been replaced by a run of good luck: Elizabeth Warren had taken out Mike Bloomberg; Bernie Sanders’ second run was proving less compelling than his first; Donald Trump’s presidency had made both rank-and-file Democrats and party elites eager for a reassuring, familiar figure in the White House; the coronavirus made everyone cherish a guy with government experience.

All of which made Biden confident and at ease in a way I  have never seen. He has come to think of his own career as a metaphor for the downtrodden of American society, because “the pundits” and pols had left him for dead politically after Iowa and New Hampshire – and indeed had scoffed at him for decades as just a small-state backslapper of no substance.

He always had the gift of attracting smart, capable people as staff. It was as if he and they understood the drill: He would empower them with his charm and salesmanship; they would educate him on the policy and legal details. Some of these political veterans had publicly kept their distance as his campaign floundered; now they are back -- literally dancing in Philly Tuesday night.

Still, he will need more than a change in the political wind to get where he wants to go. Biden thinks of himself as a skilled diplomat. He will need all of that skill and more to deal with Bernie Sanders and, just as important, his crew. Bernie and his voters will decide whether Biden’s road to Milwaukee is smooth or not – and whether the convention there will be a show or a shambles.

Sanders’ agenda may seem “pie in the sky” to Biden, but it is a meat-and-potatoes hope for millions, especially the younger voters Biden will need to defeat Trump. Wooing Bernie’s “Bros” in 2016, Hillary Clinton made a passing effort to meet Sanders partway on “Medicare for All” and free college. Biden will have to take the effort to incorporate that agenda more seriously. He touts himself as a unifier; his first test is his own party.

As centered and serious as he was Tuesday night, Biden will have to be more so as TrumpWorld comes after him. The former vice president and Delaware senator has a 48-year-long record to defend, and his instinct is to fight to defend it all. “Personal” does not begin to describe how invasive it will be, not only about his votes, speeches and decisions, but his family and son Hunter.

Biden, who has a history of garbled speaking and trouble explaining facts and sticking to them, will have to show that he can be as eloquent as he was Tuesday night in more challenging settings – notably one-on-one debates. The next will come Sunday night in Phoenix with Sanders, a cornered candidate who has little to lose. Down the road will be face-offs on stage with  the incumbent president. It’s hit-or-miss at any moment. But that’s true of Trump as well.

It’s four months until the Democrats’ Milwaukee convention; eight months until Election Day. A week is a month in politics; a year a lifetime: a long road still. But Tuesday night, in Philadelphia, Joe Biden had finally gotten to where he wanted to be.