The day after 9/11, everything changed. Realizing the nation needed a more integrated, holistic approach to domestic security, Congress created the Department of Homeland Security. Combating terrorism became job No. 1.

All this came with a caveat. From the start, Americans remained understandably concerned. Under the wrong leaders, these powerful instruments of public safety could be turned into weapons for partisan action: suppressing free speech, invading privacy, denying the right to assemble peacefully, and persecuting political opponents.