Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: (CNN) The days following the September 11, 2001, attacks were marked by political solidarity over confronting America's enemies. No longer. As the 15th anniversary of the horrific attacks approaches Sunday, the political world is bitterly divided on how to address terrorism and national security. Donald Trump dominated the GOP primaries after breaking with key elements of his party's post-9/11 ethos. He blamed former President George W. Bush, whose original response to the attacks sent his approval ratings to historic highs, for the terrorist strike. And Trump has proposed banning Muslims from entering the United States. Though he's softened the proposal somewhat in gearing up for the general election, his stance still represents a dramatic departure from Bush's visit to the Islamic Center of Washington, DC, six days after the attacks to proclaim "Islam is peace."Americans remain committed to the fight against terrorismBut that unity fizzles once Washington gets involved 
 Question:_'s decision to base his campaign around a vision of a nation under siege from foreign extremism may have contributed to the mood.

Donald Trump