Final answer:
The advent of social media has most transformed the political landscape since 1990.
Step-by-step explanation:
The advent of social media has most transformed the political landscape since 1990. Social media resources on the Internet have had a great impact on politics and government, allowing people from all walks of life to interact, share their thoughts and opinions, and mobilize in ways that were not possible before. The use of social media in political campaigns, as seen in the examples of Barack Obama's campaign in 2008, has revolutionized political organizing and communication.