WASHINGTON (AP) - The top Republican in the Senate proposed on Tuesday giving President Barack Obama sweeping new power to, in effect, unilaterally increase the nation's debt limit to avoid a first-ever default on U.S. obligations. Minority Leader Mitch McConnell, R-Ky., offered a new plan to allow the president to demand up to $2.4 trillion in new borrowing authority by the summer of next year in three separate submissions. Those increases in the so-called debt limit would automatically take effect unless both the Republican House and the Democratic Senate enact legislation specifically disapproving it. Obama would be able to veto...