BOSTON (AP) — Boston is facing a historic political pivot with the expected departure of Mayor Marty Walsh to become President Joe Biden’s labor secretary. When Walsh leaves, the city will see the elevation of the first woman and first Black Bostonian to the mayor’s office with City Council President Kim Janey stepping in on an interim basis. Janey’s rise ends a string of Irish-American mayors — all men — stretching back more than a century. And the change is unlikely to stop there: The three declared candidates in this year’s mayoral election are also all women of color.