Deal to End Senate Rift May Give Democrats Full Control in Albany

For Mr. de Blasio, who is embracing a more muscular role in state politics, the emergence of a Democratic Senate would be a political coup. The mayor took a beating in Albany earlier this year, as Mr. Cuomo seemed to relish the opportunity to trip him up.

But the mayor, whose history as a political operative has often been highlighted, chose to take a longer view. He could now gain significantly from winning a friendlier Senate, which has sometimes been an immovable political obstacle for the city.