Final answer:
The 2008 election is regarded as a realigning election due to a substantial and enduring demographic and political shift in the electorate, with increased diversity and different voting patterns.
Step-by-step explanation:
The 2008 election is considered a realigning election because it demonstrated significant changes in voting patterns that indicated a shift in the demographic and political landscape of America. A realigning election is characterized by a distinct and lasting shift in the political balance of power. The 2008 election saw increased voter turnout rates, especially among young voters and ethnic minorities, many of whom voted for the first time.
Moreover, patterns seen in previous elections, where Republican candidates would dominate rural areas and Democratic candidates would receive more metropolitan support, continued to be apparent. The Pew Research Center also noted the 2008 electorate as "the most diverse in U.S. history", indicating a broader realignment and diversification of the parties' voter bases.
The aftermath of the Iraq War and economic concerns at the time also contributed to the realignment, with voters expressing a desire for change leading to a Democratic majority in the Senate after the election.