The Northeast, once the nation’s political engine that produced presidents, House speakers and Senate giants including the late Edward M. Kennedy, is losing clout in Washington as citizens flee the high-tax region, according to experts worried about the trend. The Census Bureau reports that population growth has shifted to the South and the result is that the 11 states that make up the Northeast are being bled dry of representation in Washington. Critics blame rising taxes in states such as Massachusetts and Connecticut for limiting population growth in the Northeast to just 15 percent from 1983 to 2013, while the...