It unfolded like a perfectly scripted scene from the great British political comedy The Thick of It - but this was wincingly real.
The politician heaved himself into the privacy of his car, relieved himself of some utterly private comments and his aides were left scrambling to avoid juggling the last grenade while cleaning up the blast zone.
Gordon Brown, whatever his economic and policy experience and command of detail, has developed a reputation for bullishness - in the china-shop sense - in the political art of salesmanship.
Ultimately, voters everywhere prefer the appearance of sincerity, honesty, competence and straight-talking to raw, full-bodied and haphazard reality - whatever their stated revulsion for slickness and manipulation.
Brown's predecessor Tony Blair - respected and reviled as a consummate politician - was memorably caught on an open mic in the "Yo, Blair" episode with George W. Bush. But it was a one-off.
Neither of Brown's rivals, David Cameron and Nick Clegg, look the type to bumble the aftermath of a recorded, open-air encounter with a bread-shopping granny.
Polls show the electorate has lapped up Clegg's transparent debate tactics - his earnest appeals down the camera lens, pitches for "honesty", "fairness" and rejection of the two "old parties" - in its eagerness for change. They also show that support for the Tories is holding firm behind Cameron's largely ruffle-free performance.
This morning's debate on economic issues was already shaping as Brown's last stand, his final chance to turn around an ebbing campaign as head of an unpopular administration in power for 13 years.
The election result may require a crystal ball and degree in mazeology to predict as a range of outcomes are still possible. But Brown's personal prospects of holding onto his job appear doomed. Clegg's warning that he'd rather work with the Man on the Moon than the current Prime Minister seemed to sentence Brown to the outer galaxies as, realistically, Labour's only hope of hanging on to power is through a Lib-Lab deal.
Yesterday's gaffe surely helped seal Brown's fate as yesterday's man.