The former C.I.A. officer Valerie Plame, whose cover was blown in a leak that touched off a political scandal during the George W. Bush administration, said Thursday that she plans to run for Congress as a Democrat.

Ms. Plame, 55, is running for the northern New Mexico seat being vacated by Representative Ben Ray Luján. Mr. Luján, who had been regarded as a possible successor to Speaker Nancy Pelosi, has announced that he plans to run for Senate to replace the retiring Senator Tom Udall.

Ms. Plame, who moved to Santa Fe after leaving Washington more than a decade ago, has recently worked as a speaker and writer, but she is best known for the circumstances of her departure from the C.I.A., where she had served for two decades.

When her husband, the American diplomat Joseph C. Wilson IV, wrote an opinion essay in The New York Times in 2003 raising questions about a central underpinning for the invasion of Iraq — that President Saddam Hussein was acquiring nuclear weapons there — Ms. Plame’s identity was leaked to the news media.