Powerful Democratic former speaker Nancy Pelosi won't seek reelection to the U.S. House.

Pelosi's announcement brings to a close her storied career as not only the first woman in the speaker’s office but arguably the most powerful in American politics.

Pelosi, who has represented San Francisco for nearly 40 years, announced her decision Thursday.

Pelosi, appearing upbeat and forward-looking as images of her decades of accomplishments filled the frames, said she would finish out her final year in office. And she left those who sent her to Congress with a call to action to carry on the legacy of agenda-setting both in the U.S. and around the world.

Her departure will touch off a succession battle at home in California, where she faced a progressive challenger in next year's midterm election.

Pelosi's decision comes as a seasoned generation of political leaders is stepping aside.

Pelosi had already relinquished her leadership position three years ago, becoming speaker emerita. Democratic Party newcomers are eager to take the lead and confront President Donald Trump.