Black political power is declining in cities across the country, including Oakland, St. Louis, Cleveland and Atlanta — even as African-Americans are gaining majority status in an increasing number of suburbs.

At the same time, African-American emigration to the South has started to weaken Republican control of some deep red states.

Let’s start with Washington, D.C. The shift there (as elsewhere) is drivenboth by gentrification and by a black movement away from urban centers.

In 1957, Washington became the first large city in the United States to become majority African-American. In 1973, Congress gave home rule to the District. The first mayoral election was held in 1974, and Walter Washington, who had been appointed to the position in 1967, won it. He was the first of a series of black mayors that has continued to this day.

One area of Washington’s politics — campaign money — is already dominated by whites and has been for a long time. “D.C.’s White Donor Class,” a new study by Sean McElwee, a policy analyst at Demos, a liberal think-tank, found that among contributors of $1,000 or more to the 2014 campaign for mayor and city council campaign, “62 percent of mayoral donors and 67 percent of City Council donors are white.”