The Democratic Party struggled at the national level throughout the 1970s and ’80s — all but shut out of the White House — because it was defined by its most extreme elements: war protestors, loony peaceniks, angry black activists, crime apologists, etc. It took years of concerted effort by the Democratic Leadership Council, Bill Clinton and others to reclaim the Democrats’ reputation as reasonable and pragmatic. The Republican Party of today is stuck in the same place, defined by Rush Limbaugh, Sarah Palin, birthers, tea partiers and Joe Wilson. John McCain fell into the trap of being defined by the...