Answer:
The maps indicate that Barack Obama won the 2008 presidential election by:
C. winning key swing states won by George W. Bush in prior elections.
Barack Obama was able to win several states that had voted for George W. Bush in the previous elections, such as Florida, Ohio, and Virginia. These states were seen as key swing states and their votes were crucial to Obama's victory. By winning these states, Obama was able to secure a large number of electoral votes and win the election.