Playing the president of the United States gives Geena Davis goosebumps.

Playing the first female president of the U.S. gives her hope.

When the star of ABC's new drama, "Commander in Chief," first walked onto the Oval Office set, "I felt I was experiencing what will be an incredibly historic moment," she said.

A woman chief executive "will happen. It's just a question of when. ... That woman will do exactly what I did. She'll walk in and think, 'I'm the president. This is my office.' "

"Commander," debuts at 8 tonight. Davis plays Vice President Mackenzie Allen, a political independent who becomes chief executive when the president dies after brain surgery. Almost everyone wants her to step down.

Davis said when she read the series script, "I just jumped in, against my career-long vow that I would never do hourlong TV, because it's widely understood to be the worst lifestyle you can possibly have. ... And here I am."

The first female president.