WASHINGTON — About as many left-of-center political groups in the nation's capital call themselves liberals these days as say they're Whigs. Instead, they call themselves "progressives." What progressive means is "pretty murky," political historian Alan Brinkley said. Still, murky is an improvement over "liberal," a mainstream term in the 1960s that conservatives reduced to a dirty word in the 1980s. Pollsters said the shift to "progressive" sheds the onus of the liberal label and enables left-of-center groups and candidates to fight again. Although the term "progressive" has a distinguished early-20th-century history that includes reformers Theodore Roosevelt and Woodrow Wilson, uncertainty...
