“There is the next frontier in political advertising: your personal location data, collected from apps you’ve downloaded that then take this sensitive information and sell it to third parties — including political campaigns. Love it or hate it, digital strategists see this location data as part of the future of political campaigns, as candidates and advocacy groups harness your personal whereabouts and leverage it to try to win your support. One campaign might know if you’ve passed by one of their lawn signs recently. Another might track whether you’ve been in a specific Catholic church in Dubuque, Iowa. Forces behind Trump, who three years ago said he considered data to be “overrated” in politics, are exploring this next iteration of digital campaign tools. And with the incumbent president’s vastly superior resources and innate appetite for digital experimentation, many leading Democrats are concerned that it is the GOP — not the digitally pioneering party of Barack Obama — that is mastering Silicon Valley’s tricks ahead of what’s expected to be the most expensive US presidential election ever.”

Source : How Trump allies are using your phone’s location to try and win your vote – Vox