Jean Smart knows a bit more than “24” fans about the future of first lady Martha Logan, the character she plays on the Fox series. But not much more.

Nobody on the round-the-clock thriller, notorious for its high body count, can ever be sure if they’ll survive until the final second of the entire season is ticked off.

On this day, Smart is shooting the 17th and 18th hours of federal agent Jack Bauer’s latest struggle to save the country from terrorists in just 24 hours – so she knows she’s made it that far. But come next week, she could easily become the late Martha Logan.

“I just hope if she goes, she goes in a real big way and takes a few people with her,” Smart laughs, noting her teenage son, Connor, is “disappointed I haven’t shot anybody yet.”

Smart said she believes the show’s writers when they say “they kind of do it on the fly,” without a predetermined story line for the entire season.

In fact, the following day, co-executive producer Howard Gordon announced the writing team had just come up with “something that actually reverses very much where we were going.”

He said they’re re-scripting the last four episodes because “what’s wonderful about this show is the end usually lies somewhere that’s not in the obvious places.”

But a comment Gordon makes about the Logans’ discordant marriage being “one of the highlights of this year” seems to imply that she’ll make it to the season finale – at least to the first commercial break, anyway.

Smart, 46, is best known on TV as Charlene Frazier-Stillfield from the sitcom “Designing Women.” More recently, she won back-to-back Emmys for her guest appearances on “Frasier,” and had a recurring role in the crime series “The District.”

The troubled and troublesome Martha Logan has been compared to Martha Mitchell, the outspoken wife of Nixon-era attorney general John Mitchell, who was trashed as delusional for not keeping her mouth shut during the Watergate scandal.

Although the producers acknowledge that influence, Smart says it didn’t really figure into her interpretation.

“How did that get started?” she puzzles. “I hope I don’t remind people of Martha Mitchell, bless her heart, wherever she is.”