How does big data become a game-changer in politics?

Big data contains a vast amount of personal data that can be easily accessed, filtered and evaluated by large companies, governments and political parties that can pay for it nowadays. So, the choices and preferences of the voters can be interpreted strategically. Articles about Obama's presidential campaign have been released. Consider that the back office understands facts, interprets data and plans action (political messages and decisions), with a front office for collecting data, views and opinions, and linking with people using any media , especially the omnipresent social media, and other large-scale platforms. I suggest you to read "How Facebook is changing democracy" on Financial Times.