Abstract
Successful modern democracies act to balance the twin obligations of maintaining secure and tolerant environments for their citizens. When faced with external threats such as global terrorism, democracies respond in a pendulum fashion—acting initially by giving security precedence over other values and then swinging back towards moderation, the pursuit of tolerance, and the promotion of policies that match the preferences of the median voter in society. Understanding this behavior helps to explain shifts in U.S. security policy since 9/11, and suggests fruitful avenues for research in political psychology.