'It might work too well': the dark art of political advertising online

Digital campaigns have evolved from banner ads 20 years ago to Cambridge Analytica harvesting our Facebook data. Has the rise of micro-targeting become a threat to democracy?

Alan Gould was hitting a wall. It was the late 1990s, and the political advertising operative had an idea about using a relatively newfangled tool - banner ads on web sites - to promote political candidates. "It was pretty clear to me at the time that the ability to target and tailor messaging was perfect for political campaigns," Gould recalled recently. "I did a whole presentation on the internet and the power to connect, track, do fundraising, target."

But when Gould finished his pitches, he would be met with blank stares. "I was a very lonely pied piper," he says.