LONDON (AP) — Chris Wylie can't prove the work he did for Cambridge Analytica helped Donald Trump win the 2016 presidential election, but he thinks he has pretty good evidence.

While working for the political consulting company from 2013 to 2015, Wylie's team spoke to Americans in focus groups to identify deep-seated concerns. Then they tested ways to tap into those fears through social media. The slogans they developed later became the catchphrases of the Trump campaign, he says.

Wylie, a 28-year-old Canadian, is at the center of allegations that Cambridge Analytica improperly used data from more than 50 million Facebook users to identify voters who might be sympathetic to Trump's message and target them with social media messages.