Final answer:
The impact of the 9/11 attack by Al-Qaeda on Millennials' political socialization most clearly demonstrates the effect of political polarization on the formation of political views.
Step-by-step explanation:
The impact of the 9/11 attack by Al-Qaeda on Millennials' political socialization most clearly demonstrates the effect of political polarization on the formation of political views. Following the 9/11 attacks, there was an increase in partisanship and a shift towards more conservative or liberal ideologies among citizens, which indicates a polarizing effect on political views. Some scholars believe that this shift may have a lasting impact on the political beliefs of Millennials.