President Donald Trump’s border wall started out years ago as a “memory trick” for a would-be presidential candidate who was considered “undisciplined.”

Speaking to the New York Times, former Trump political adviser Sam Nunberg recalled how he coordinated with fellow adviser Roger Stone as they came up with the wall idea as a tool to remind Trump to talk about his plans to crack down on illegal immigration. With Trump following Nunberg and Stone’s advice and mentioning the wall in his rallies, the would-be president got “rapturous cheers” from conservative voters, leading him to continue bringing it up as he pushed forward with his campaign.