Editor's Note: David Axelrod, a senior CNN political commentator and host of "The Axe Files," was senior adviser to President Barack Obama and chief strategist for the 2008 and 2012 Obama presidential campaigns. The opinions expressed in this commentary are his. View more opinion articles on CNN.
(CNN) - The fireworks between Elizabeth Warren and Bernie Sanders after the CNN debate on Tuesday night took me back to another heated confrontation between presidential candidates I witnessed, not in public but on an airport tarmac in Washington, DC.
It was December 2007. With the Iowa caucuses weeks away, Barack Obama was moving up in the polls and Hillary Clinton's campaign was ratcheting up its attacks. Amid the offensive, one of Clinton's key supporters unloaded, telling reporters that Obama's use of cocaine in his teens would render him unelectable.
Far from wounding Obama, the salvo backfired. Obama had written years earlier in his memoir, "Dreams from My Father," about his teenage drug use. The resurfacing of it late in the run up to the caucuses was read by many as a cheap shot -- with vaguely racial implications -- and as a sign of growing anxiety within the Clinton ranks.
That story was raging when we headed to the airport for a flight from Washington to Iowa for a campaign debate. As we approached the entrance to the charter terminal to catch our flight, we noticed a young man in a suit, frantically running in our direction. He identified himself an aide to Sen. Clinton, whose plane coincidentally was parked directly next to ours.
"Senator Clinton would like to have a word with you, sir," the young man told us breathlessly.
As the Clinton aide walked away, Obama asked me, "What do you think this is about?" I told him that she would apologize for her supporter's remarks and disavow any knowledge or awareness that such a blast was coming. And then her campaign would leak the conversation to try and stem the tempest the attack had created.
Obama and his traveling aide, Reggie Love, approached the Clinton plane where she and her longtime traveling aide, Huma Abedin, greeted them on the tarmac. Obama's spokesman Robert Gibbs and I hustled up the stairs of the Obama plane to watch from a window.
The conversation seemed to begin calmly enough as Clinton spoke and Obama listened. Then Obama responded. And all hell broke loose.
Clinton's face hardened. She spoke animatedly and jabbed a finger in Obama's direction. When he responded by putting a hand on her shoulder, she pointedly brushed it away. This went on for 10 minutes, as their two aides, standing nearby, toed the ground and averted their eyes, looking as if they wanted to be anywhere else (like Tom Steyer did Tuesday night, when he walked into the Warren-Sanders scrap).
"What the hell is going on over there?" I asked Gibbs.
"I don't know but she doesn't look too happy," he said.
Later, we learned that Clinton had proffered the expected apology and disclaimer. But when Obama raised other actions by her campaign he felt were out of bounds, Clinton became incensed and disgorged her own litany of complaints about our campaign tactics.
When Obama returned to the plane, he flopped down in a seat, a look of disbelief on his face as he recounted the conversation.
"For the first time in this campaign, I saw fear in her eyes," he said.
Obama and Clinton were friends before the campaign of 2008. They would be allies after. Indeed, President Obama would appoint Clinton as his secretary of state.
But when ambitions clash and the days are ticking down to the critical first contest of the campaign season, friendships are tested and tempers fray.
Bernie Sanders and Elizabeth Warren called themselves friends and allies before this campaign. Their private meeting in 2018, the facts of which are now in dispute, was all about which of them could best marshal the progressive movement as a candidate in 2020.
That question unresolved, they now are competing for primacy among the progressive bloc of Democratic Party voters, and time is short. The Iowa caucuses, little more than two weeks away, may well define who will carry that banner forward.
It isn't clear how or if their heated open mic moment after the debate -- or Warren's charge that Sanders privately questioned a woman's chances to win -- will affect the outcome of their respective campaigns.
But a clash between these erstwhile allies, who avoided confrontation throughout 2019, seemed inevitable. And it's a sure sign that voting is near.