Sens. Barack Obama and Hillary Clinton took part in a Democratic presidential primary debate in Iowa on Dec. 13, 2007, not long after a testy exchange on the tarmac at Reagan National Airport. (Charlie Neibergall/AP)

It was December 2007, and the Democratic race for the presidential nomination had taken a bit of a nasty turn. Billy Shaheen, then co-chair of Hillary Clinton’s New Hampshire campaign, had speculated to The Washington Post that Republicans would attack Sen. Barack Obama on the drug use the candidate had admitted to on the trail and in “Dreams From My Father,” his 1995 memoir. As Shaheen put it: “It’ll be, ‘When was the last time? Did you ever give drugs to anyone? Did you sell them to anyone?’ There are so many openings for Republican dirty tricks.”

The next day, Obama and Clinton were both at Reagan National Airport on their way to Iowa for a debate, and the candidates met on the tarmac for what became a brief but heated conversation. Then-Obama personal aide Reggie Love witnessed the event and describes it in his new memoir:

“I want to apologize for the whole Shaheen thing,” Clinton said. “I want you to know I had nothing to do with it.”

The candidate very respectfully told her the apology was kind, but largely meaningless, given the emails it was rumored her camp had been sending out labeling him as a Muslim. Before he could finish his sentence, she exploded on Obama. In a matter of seconds, she went from composed to furious. It had not been Obama’s intention to upset her, but he wasn’t going to play the fool either. To all of us watching the spat unfold, it was an obvious turning point in our campaign, and we knew it. Clinton was no less competitive or committed to a cause than Obama, and the electric tension running through both candidates and their respective staffs reflected the understanding that she was no longer the de facto Democratic candidate. Her inevitability had been questioned. . . .

I remember Obama telling me later that day that he knew he was going to win the nomination after that moment on the tarmac, because Clinton had unraveled, and he was still standing and keeping his cool. It was just the confidence boost he needed.

— from “Power Forward,” by Reggie Love

And yes, Shaheen resigned from his campaign post that day, too. “I made a mistake and in light of what happened, I have made the personal decision that I will step down,” he said in a statement.

Read more from Book Party:

Review of Reggie Love’s “Power Forward: My Presidential Education”

The time Obama walked in on a staffer who had a friend in bed