WASHINGTON — A quarter-century ago, a Democratic president celebrated “the end of welfare as we know it,” challenging the poor to exercise “independence” and espousing balanced budgets and smaller government. The Democratic Party capped a march in the opposite direction this week.... ...The new Democratic stance is “a long cry from the days of ‘big government is over,’” said Margaret Weir, a political scientist at Brown University.... ...Republicans’ increasing efforts to define themselves as a party of the working class, has scrambled the politics of economic policy across the ideological spectrum....