One of the Key Strategies That Helped Barack Obama Win

One of the key strategies that helped Barack Obama win both of his elections for President was

A) investing heavily in direct mail to reach older voters in their homes.
B) identifying and micro-targeting potential younger voters through their e-mail and social media accounts.
C) traveling to less populated parts of the country to target marginalized rural voters.
D) putting lots of resources into television advertisements in conservative states to win them over.