Question: Which state did Joe Biden represent in the Senate for 36 years before becoming Vice President in 2009?

full_context: Document 1: Political positions of Joe Biden: Joe Biden served as the Vice President of the United States from 2009 to 2017. He served in the Senate from 1973 until 2009 and made his second run for President of the United States in the 2008 presidential election as a Democrat. Biden was announced as Democratic presidential nominee Barack Obama's running mate on August 23, 2008, and was elected Vice President on November 4, 2008.
Document 2: Hunter Biden: Robert Hunter Biden (born February 4, 1970) is the second son of former U.S. Vice President Joe Biden and his first wife, Neilia Biden. He is a partner at Rosemont Seneca Partners, LLC and is Counsel to Boies, Schiller, Flexner, LLP, a New York-based-law firm.
Document 3: United States Senate election in Maine, 2000: The 2000 United States Senate election in Maine was held November 7, 2000. Incumbent Republican U.S. Senator Olympia Snowe was re-elected to a second term, defeating Democratic candidate Mark Lawrence.
Document 4: United States Senate election in Oklahoma, 2002: The 2002 United States Senate election in Oklahoma was held on November 5, 2002. Incumbent Republican U.S. Senator Jim Inhofe won re-election to a second term.
Document 5: Electoral history of Joe Biden: Electoral history of Joe Biden, 47th Vice President of the United States (2009–2017), United States Senator from Delaware (1973–2009). To date Joe Biden has not lost an election.
Document 6: Joe Biden presidential campaign, 1988: The 1988 presidential campaign of Joe Biden, the longtime Democratic United States Senator from Delaware and eventual 47th Vice President of the United States began on June 1987. He ran for President of the United States in the 1988 United States presidential election. He was considered one of the potentially strongest candidates in the field. However, in September 1987, newspaper stories stated he had plagiarized a speech by British politician Neil Kinnock. Other allegations of past law school plagiarism and exaggerating his academic record soon followed. Biden withdrew from the race later that month.
Document 7: United States Senate election in Hawaii, 2004: The 2004 United States Senate election in Hawaii took place on November 2, 2004 alongside other elections to the United States Senate in other states as well as elections to the United States House of Representatives and various state and local elections. Incumbent Democrat U.S. Senator Daniel Inouye won re-election to an eighth term.
Document 8: United States Senate election in Maryland, 2006: The 2006 United States Senate election in Maryland was held on Tuesday, November 7, 2006. Incumbent Democratic U.S. Senator Paul Sarbanes, Maryland's longest serving United States Senator, decided to retire instead of seeking a sixth term. Democratic nominee Ben Cardin won the open seat.
Document 9: United States Senate election in New Jersey, 2006: The 2006 United States Senate election in New Jersey was held on November 7, 2006. Incumbent Democratic U.S. Senator Bob Menendez was elected to represent New Jersey in the United States Senate for a six-year term which ended in January 2013. The seat was previously held by Democratic Governor of New Jersey Jon Corzine. After he stepped down from his Senate seat and was sworn in Governor, Corzine appointed Rep. Menendez, who was sworn in on January 18, 2006. Menendez was challenged by Republican Thomas Kean, Jr. and seven other candidates. Filing for the primary closed on April 10, 2006. The primary election was held on June 6, 2006. Menendez became the first Hispanic to hold a U.S. Senate seat from New Jersey, and was the first Latino elected to statewide office in the state.
Document 10: United States Senate election in Delaware, 1972: The United States Senate election in Delaware, 1972 was held November 7, 1972. Incumbent Republican United States Senator J. Caleb Boggs ran for a third term in the United States Senate. Boggs faced off against Joe Biden, a New Castle County Councilman. Though Senator Boggs was expected to easily win a third term over the then-unknown Biden, it ended up being the closest Senate election in 1972, and Biden narrowly beat out Boggs by a little over three thousand votes, winning what would be his first of seven terms.
Document 11: Beau Biden: Joseph Robinette "Beau" Biden III (February 3, 1969 – May 30, 2015) was an American attorney, officer in the Army Judge Advocate General's Corps, and politician from Wilmington, Delaware. He was the eldest of three children from the marriage of former U.S. Vice President Joe Biden and his first wife, Neilia Biden. He served as the Attorney General of Delaware, a major in the Delaware Army National Guard, and a member of the Democratic Party.
Document 12: United States Senate election in Alaska, 2002: The 2002 United States Senate election in Alaska was held on November 5, 2002. Incumbent Republican United States Senator Ted Stevens ran for and won a sixth term in the United States Senate. He faced perennial candidate Frank Vondersaar, the Democratic nominee, journalist Jim Sykes, the Green Party nominee, and several other independent candidates in his bid for re-election. Ultimately, Stevens crushed his opponents to win what would be his last term in the Senate, allowing him to win with the largest margin of victory for any Senate election in Alaska, as well as the highest percentage of the vote in any of his elections.
Document 13: United States Senate election in New York, 2006: The 2006 United States Senate election in New York was held November 7, 2006. Incumbent Democratic U.S. Senator Hillary Rodham Clinton won, by a more than two-to-one margin, a second term representing New York in the United States Senate. Clinton was challenged by Republican John Spencer, a former Mayor of Yonkers, New York. Spencer won his party nomination by defeating former national security staffer K. T. McFarland in a primary.
Document 14: United States Senate election in Delaware, 2002: The 2002 United States Senate election in Delaware was held on November 5, 2002. Incumbent Democratic U.S. Senator Joe Biden won re-election to a sixth term.
Document 15: Joe Biden: Joseph Robinette "Joe" Biden Jr. ( ; born November 20, 1942) is an American politician who was the 47th Vice President of the United States from 2009 to 2017. A member of the Democratic Party, he represented Delaware as a United States Senator from 1973 until becoming Vice President in 2009.
ground_truth: Delaware