Independently verified. Warren is a Senate Co-Chair of the Expand Social Security Caucus (with Bernie Sanders) and jointly introduced the Social Security Expansion Act, S.393 in the 118th Congress (introduced Feb 13, 2023), a bill matching the promise exactly: it would raise benefits ~$2,400/year, extend solvency 75 years past 2096, and apply the payroll tax to income (including capital gains) above $250,000. This is genuine, sustained leadership beyond a single supporting vote: she co-chairs the dedicated caucus and has repeatedly co-introduced the flagship bill (117th, 118th, and 119th Congresses). Congress.gov lists Sanders as formal primary sponsor and Warren among several cosponsors, but her caucus co-chairmanship and co-introduction role make CHAMPIONED, not merely ATTEMPTED, the correct label. The promise to PASS the Act was not fulfilled — S.393 was read twice, referred to the Committee on Finance, never received a committee or floor vote, and died at the end of the 118th Congress — so it falls short of FULL. This standard is party-neutral: a legislator of either party who co-chairs the relevant caucus and repeatedly co-introduces the matching bill, but does not get it passed, warrants CHAMPIONED. The prior rating's outcome and confidence stand; the unverifiable Newsweek citation was replaced with the corroborating Sanders press release.