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Political campaigns know a lot about voters. That became obvious when news broke that Cambridge Analytica improperly mined data from as many as 87 million Facebook users. The company’s CEO, Mark Zuckerberg, is on Capitol Hill this week to answer questions about it. Cambridge Analytica has also claimed credit for Republican wins in Colorado in 2014.

To get perspective on what campaigns know about voters, and how they legally use social media, Colorado Matters talked with a 25-year veteran of polling and political data. David Flaherty leads Magellan Strategies, a Republican-leaning polling and campaign consulting firm in Louisville.