Her family announced the death in a statement, saying she had battled pneumonia since January. In a recent Facebook post, Ms. Tauscher said she was also being treated for a complication from her 2010 surgery for esophageal cancer.
A former investment banker and stockbroker, Ms. Tauscher was one of the first women to hold a seat on the New York Stock Exchange, and — at 25 — the youngest. Elected to the House in 1996, she represented an eastern swath of San Francisco suburbs previously controlled by the Republican Party, and espoused a pro-business, socially liberal political philosophy that Time magazine dubbed “Tauscherism.”
Known for a witty and sometimes blunt speaking style, Ms. Tauscher she said she drew on her Wall Street experience to cut deals, often across the aisle, and served as chairwoman of the centrist New Democrat Coalition.
She spent much of her time in Congress focused on missile defense and nuclear weapons issues, a specialty she developed in part because her district included Lawrence Livermore National Laboratory, a center of nuclear weapons research, as well as Travis Air Force Base and the California campus of Sandia National Laboratories.
Ms. Tauscher chaired the Armed Services subcommittee on strategic forces and, after the Democrats took control of the House in 2006, often served as Speaker pro tempore, presiding over contentious debates on climate change, covert wiretapping and the 2008 financial bailout.
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“She could often be seen on C-Span, hammer in hand, peering sternly at colleagues over her glasses, as she maneuvered deftly through a barrage of parliamentary inquiries or disputes among members about who was controlling the floor at any particular moment,” New York Times reporter David M. Herszenhorn wrote in June 2009, after Ms. Tauscher wielded the gavel one last time before joining the State Department.
As undersecretary of state for arms control and international security, she was credited with playing a key role in arms-reduction talks with Russia, which culminated with the New Strategic Arms Reduction Treaty in 2010.
The pact marked the first major nuclear-arms control treaty between both sides in nearly two decades, capping the number of deployed, long-range nuclear warheads and setting new limits on nuclear missiles, bombers, launchers and submarines.
Ms. Tauscher was “the most important person in getting us to the negotiation of the New START Treaty,” former secretary of state Hillary Clinton told Politico on Tuesday. “In my opinion, it would not have happened without her.”
Her work on the treaty coincided with her cancer diagnosis and, by the time the pact was ratified in December 2010, Ms. Tauscher was lying in a hospital bed. She later said she spent days “croaking on the phone,” speaking with Clinton and Sens. John F. Kerry (D-Mass.) and Dianne Feinstein (D-Calif.), to urge them to force a vote on the pact.
In February 2012, she took a newly created part-time position, serving for several months as the State Department’s special envoy for strategic stability and missile defense. Her esophagus had been “ripped out” of her chest, she said, rebuilt with tissue taken from her stomach, and although she was still unable to lie flat, she was strong enough to keep working.
She told the San Francisco Chronicle that amid her recovery, she had fantasized about the demise of her tumor, imagining that the mass of cells was gorging on her toxic chemotherapy treatment. “It was really very perverse,” she said. “Here I am the undersecretary for arms control and national security, and I’m basically using a chemical weapon and radiation. Chemical weapons? I’m for them! Radiation? I’m for that, too!”
The oldest of four children, Ellen O’Kane was born in Newark on Nov. 15, 1951, and raised in neighboring Harrison, N.J. Her mother was a secretary, and her father was the shop steward for the meatpackers union, and later manager of a supermarket.
Ms. Tauscher was the first member of her family to attend college, receiving a bachelor’s degree in elementary education from Seton Hall University in 1974. There were no jobs in teaching, she later said, so she joined Bache & Co. in New York and began trading municipal bonds.
She later served as an officer of the American Stock Exchange, and in 1989 married businessman William Y. Tauscher. They moved to the Bay Area, where after the birth of their daughter, Katherine Tauscher, Ms. Tauscher formed the ChildCare Registry to help parents research the backgrounds of care providers.
Ms. Tauscher also became a Democratic fundraiser, and co-chaired Feinstein’s first two Senate campaigns before entering the 1996 House race, attacking Republican incumbent Bill Baker for opposing gun control and abortion. She won with 49 percent of the vote.
In office, Ms. Tauscher served on the Transportation and Infrastructure Committee and often battled with her party’s left wing, which rebuked her for voting in favor of the Iraq War (she later opposed it) and backing legislation to support free-trade agreements and reduce the estate tax.
When Rep. Nancy Pelosi (D-Calif.) ran for minority whip in 2001, Ms. Tauscher was the only California Democrat to oppose her, siding with a more moderate rival, Steny H. Hoyer of Maryland. They had repaired their relationship by the time Pelosi named Ms. Tauscher Speaker pro tempore.
Ms. Tauscher went on to serve on corporate and nonprofit boards, including the University of California Board of Regents, and was vice chair of the Atlantic Council’s Scowcroft Center for Strategy and Security.
Her marriages to William Tauscher and James Cieslak, a retired Delta Air Lines pilot, ended in divorce. In addition to her daughter, survivors include a brother and two sisters.
In recent years, Ms. Tauscher wrote op-eds and gave interviews in favor of redistricting reform, calling it a cure-all for a disjointed Congress. She co-founded the organization #YouDrawTheLines2021, which champions independent, nonpartisan redistricting commissions to resolve what she described as a “constitutional crisis.”
“The Founding Fathers . . . did not foresee that it would be possible to create congressional districts and assign them to parties where the person in the seat is fungible and the party owns that seat for 10 years during the time between redistrictings,” she told the Los Angeles Times in 2015. “That’s why I think you have such tremendous voter apathy, why you have people believe their vote doesn’t matter and the sense that it’s all rigged.”
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