Diane McBride was a one-time appearing guest character who appeared in the Season Two opening episode "Honeymoon Express". The part of Diane was played in the episode by Alice Adair.
About Diane[]
Diane McBride was the daughter of an influental U.S. Seanator and newlywed-wife of Tom MacBride, whom Sam was leaped into to save her from being murdered by her ex-hus a French organized crime figure and espionage operative named Roget.
Tom, the leapee, was trying to influence his wife to study hard to pass her law bar exam, to ensure that she will win her late father's seat so that she would be on the Senate Commission that ensures approval for the funds needed to allow Project Quantum Leap to continue.
In all of this, when it's also revealed that several senators, along with Al had hoped for Sam to be able to influence her to contact her father, an influental U.S. Senator, who's seat she eventually runs for, but loses, in 1966, and to get him to convince the President to call off the U-2 mission, Sam will have stopped the event in which the U-2 spy plane, which the U.S. flew over Russia by Gary Powers, was to be shot down.
The event contributes to the breakdown of U.S-Soviet relations and extends the Cold War for decades. Al tells Sam that Dianne's father was one of President Eisenhower's golfing partners.
While Sam isn't able to change the fateful events leading to the U-2 plane bombing, he is able to change things for the better concerning the Project Quantum Leap re-funding, as he corrects one her answers, which, in the original course of events leading to the bar exam, influenced the rest her answers on it, as, with this time, she passes it, which, in turn, Dianne has gone on to become a U.S. Senator and is now the Committee Chairman, replacing the antagonistic Senator Weitzman (played by Warren Frost), whom she lost the 1966 Seante race to, and had mocked the whole importance of the mission.
Dianne, who all of sudden appears in Weitzman's chair in the Commission proceedings, says that the project's ambitions are noble and thus worthy of renewed funding.