The prime minister, who was taking questions from Asda staff at a headquarters in Leeds, was asked what his worst fear about the upcoming general election was.
After explaining he was most afraid of an SNP government backing up a Labour government, he meant to say next week's election was "country-defining" – but instead made an embarrassing mistake.
"This is a real career-defining, country-defining election that we face," he said, immediately correcting himself.
As it happened, the gathered press at the event laughed out loud at the obvious gaffe.
It's been seized upon by Labour election strategist David Axelrod, who said it was a "Freudian slip".
It confirmed some people's beliefs that Cameron is a career politician.
We bet Cameron knew he had made a mistake as soon as it happened.
Jamie Ross is a Scotland reporter for BuzzFeed News and is based in Edinburgh.
Contact Jamie Ross at firstname.lastname@example.org.
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