CHARLOTTE, N.C. — I remember the first time I realized that Barack Obama was not going to be another Bill Clinton. Everyone assumed that the Secretariat from Illinois was the natural heir to the Secretariat from Arkansas. But Barry was only out of the gate for a day in 2007 before it became apparent that, while the senator had a bouquet of talents and several virtues that Clinton would never possess, he was not quite Bill’s match as a political natural.

On his first Iowa campaign trip, Barry was irritated. (Michelle had made him quit smoking). He was hungry. (He had eaten only trail mix.) He was indignant. (Why would press pests care what he looked like shirtless in Hawaii?)

When the diffident debutante ended up in the deserted AmericInn’s lobby in Iowa Falls on an icy Saturday night with reporters and a few six-packs, he did not seize the opportunity to seduce, as Bill would have. Clinton probably would have chatted with one reporter about Gabriel Garcia Marquez, another about economic philosophy and a third about prowling the Arkansas backwoods to find antique cameos for Hillary.

Barry, for his part, looked around with dazed distaste and scurried up to his room. He seemed oddly conflicted about politics. That ambivalence started with the first political speech he gave at Occidental College, when he felt both elation at his ability to rouse with words and disdain at how easy it was. It became an exhausting pattern: Get people wildly excited and then withhold the excitement. Avoid sound bites and visceral connections because political games are beneath you. Instead of surfing the magic and using it to cow the opposition, Obama would retreat inside himself at crucial moments, climbing back to his contemplative mountaintop.

He rationed his smile, his eloquence and his electricity, playing the dispassionate observer, delegating, dithering and rushing in at the last moment to try to save the day. A cold shower to Bill’s warm bath. While Clinton aides had to act like sheepdogs, herding the boss offstage as he tried to linger and schmooze issues with crowds, Obama needs to be alone and decompress even after meeting with a few people.

Last week, Republicans struggled to answer the Dada question about Mitt Romney: “Can he be human?” This week, Democrats struggle to answer the Dada question about the once-thrilling Obama: “Can he be exciting?” (Nobody ever asked either question about Bill.)

After running last time as the stake in the heart of the dysfunctional, draining and seemingly indestructible Clinton dynasty, Barry has had to humble himself and ask for the help of the man his camp painted as racist and intemperate in 2008. During that race, Bill literally carried an 81-page list of perceived insults by Obama to Hillary. It is the great psychodrama of this convention: Will the shrewd and diabolical Bill buoy Barry or puncture him? Will he be generous or — like all those 2016 strivers at the Republican convention — self-obsessed?

“We don’t need Clinton the man,” said one Obama honcho as they nervously await the draft of Bill’s speech. “We need Clinton the myth.”

The two tall, left-handed, silver-tongued baby boomers both grew up not knowing their fathers. But while the disciplined Barry became self-reliant, with little patience for neediness or insincerity, the undisciplined Bill became self-indulgent, a maw of need and maestro of faux sincerity.