RITIKA SINGH and BENJAMIN WITTES – Political parties in the United States, like a spatting couple in a bad marriage, have been fighting over the law of counterterrorism for more than a decade. And like the spatting couple, they have developed an almost rote script for their fight. The script has a logic of its own. It is a comfortable one for both spouses—and the fight is soothing in its own way. Republicans and Democrats alike wrap up some portion of their party’s identity and self-image in the conflict over national-security policy. The fight gives each side the impression—and the confidence—that the other endangers America. And it gives each side something to tell voters about why they should vote one way rather than another.