In announcing plans to end Saturday mail delivery, Postmaster General Pat Donahoe himself posed the key question yesterday: “Is this legal?” Donahoe’s answer, naturally, was yes, hinging on a rather complicated analysis of the impact of congressional spending legislation (more about that in a moment). Official U.S. Postal Service talking points obtained by Federal Times offer a more straightforward explanation: USPS leaders are under orders from the agency’s board to accelerate cost-cutting measures; they believe they have the authority to go to five-day mail delivery on their own; and they are hoping that Congress won’t take any action to stop…