WASHINGTON – Sen. Daniel Inouye of Hawaii, the influential Democrat who broke racial barriers on Capitol Hill and played key roles in congressional investigations of the Watergate and Iran-Contra scandals, died Monday. He was 88.

Inouye, a senator since January 1963, was currently the longest serving senator and was president pro tempore of the Senate, third in the line of presidential succession. His office said Monday that he died of respiratory complications at a Washington-area hospital.

Senate Majority Leader Harry Reid announced Inouye’s death on the Senate floor.