A plan by the Senate's two top leaders to allow President Obama to raise the debt limit without congressional approval is emerging as the most likely strategy to avoid a looming federal default. The plan being drafted by Senate Minority Leader Mitch McConnell of Kentucky and Majority Leader Harry Reid of Nevada would lock in roughly $1.5 trillion in deficit reduction over the next ten years — a figure considerably smaller than Republican leaders or President Obama had been seeking. Administration officials have said they still would prefer a more sweeping deal on the deficit, but they signaled the idea...