As lawmakers across the nation begin the once-a-decade process of redrawing their congressional boundaries, a significant migration of Blacks from cities to suburbs is having a widespread political impact.

According to newly released census numbers, eight of the nation’s top majority-black districts lost an average of more than 10 percent of their African American populations. That will provide an opportunity for Republican lawmakers, who control an increasing number of statehouses following last fall’s elections, to reshape districts in suburban swing areas of Michigan, Pennsylvania, Ohio, Georgia and elsewhere.

Dozens of seats could become easier for Republicans to hold on to, with a half-dozen or so becoming prime pickup opportunities for the party, according to political strategists.