Two top senators on Tuesday introduced a resolution giving President Obama explicit authorization to continue aiding the NATO mission in Libya, seeking to strengthen the White House’s hand at a key moment in the brewing constitutional tug of war with Congress. Sen. John F. Kerry, Massachusetts Democrat, who is Senate Foreign Relations Committee chairman, and Sen. John McCain, Arizona Republican, who is the ranking GOP member on the Senate Armed Services Committee — and, coincidentally, the last two losing presidential nominees — are co-sponsoring the resolution, which would grant Mr. Obama “limited” authorization to continue using force. “This is not...