After retrieving control of Congress for the first time in a dozen years, Democrats will set out to redefine the domestic agenda through policies they say would address the economic needs of middle- and working-class Americans. Striving for a few quick legislative victories in January and longer-term goals whose details -- and viability -- are not yet certain, Democratic lawmakers want to shift the dialogue on Capitol Hill to workers' pay, college tuition, health-care costs, retirees' income and other issues that touch ordinary families. Their success is not assured. Democrats will hold a tenuous 51 to 49 majority in the...