'The White House Plumbers' was a covert unit established by which US President, to stop political leaks?

The White House Plumbers, sometimes simply called the Plumbers, was a covert White House Special Investigations Unit, established July 24, 1971, during the presidency of Richard Nixon. Its task was to stop the leaking of classified information, such as the Pentagon Papers, to the news media. Its members branched into illegal activities while working for the Committee to Re-elect the President, including the Watergate break-in and the ensuing Watergate scandal.

On Thanksgiving evening of 1972, David Young arrived home from his planning at the Special Investigative Unit, when his grandmother asked him, "What do you do at the White House?" He replied, "I am helping the president stop some leaks." She exclaimed, "Oh, you're a plumber!". Young, Liddy, and Hunt then put up a sign on their office with the title "The Plumbers" but it was taken down since their covert operations were supposed to be top secret. Still, the name stuck for the group.