'The Presidents' Gatekeepers' Lessons: Never Hang Up On The First Lady (VIDEO)

They say that behind every great man is an even greater woman -- and that goes for the President and his First Lady as well.

We've got an exclusive sneak peek at "The Presidents’ Gatekeepers," Discovery Channel's two-part, four-hour special (premieres Wed., Sept. 11 and Thurs., Sept. 12 at 9 p.m. ET) featuring all 20 living White House Chiefs of Staff sharing never-before-told stories from their days in the White House. The special spans nine administrations and 50 years, and has some particularly fascinating facts about Ronald Reagan's administration. (Did you know his famous "Tear down this wall!" speech almost didn't happen?)

Apparently Reagan's second Chief of Staff Donald Regan made the grave mistake of not realizing that First Lady Nancy Reagan was the President's closest confidante. "He ended up getting fired. He ended up getting fired by the President when he hung up the telephone on the First Lady. That's not just a firing offense -- it may be a hanging offense!"

"He never worried about anything. She worried about everything," Ken Duberstein, Reagan's fourth Chief of Staff, says. "The famous expression that he used, 'Trust but verify' -- he was the trust and she was the verify."

And her job as First Lady became even more important after the attempted to assassinate her husband in 1981.

James Baker, Reagan's first Chief of Staff, said, "Her political antenna and her antenna particularly about personnel were extraordinarily sensitive. She was his protector and she was very good at it."

The lesson? No matter how much power you think you have, don't ever hang up on the First Lady.

Tell us: Are you excited to hear more stories from "The Presidents' Gatekeepers"?

"The Presidents' Gatekeepers" two-night, four-hour event premieres Wed., Sept. 11 and Thurs., Sept. 12 at 9 p.m. ET on Discovery Channel.