Characteristics as senator,

With a net worth between $59,000 and $366,000, and almost no outside income or investment income, he was consistently ranked as one of the least wealthy members of the Senate. Biden stated that he was listed as the second poorest member in Congress, a distinction that he was not proud of, but attributed to being elected early in his career. Biden realized early in his senatorial career how vulnerable poorer public officials are to offers of financial contributions in exchange for policy support, and he pushed campaign finance reform measures during his first term.


During his years as a senator, Biden amassed a reputation for loquaciousness,with his questions and remarks during Senate hearings being especially known for being long-winded. He has been a strong speaker and debater and a frequent and effective guest on the Sunday morning talk shows. In public appearances, he is known to deviate from prepared remarks at will. According to political analyst Mark Halperin, he has shown "a persistent tendency to say silly, offensive, and off-putting things"; The New York Times writes that Biden's "weak filters make him capable of blurting out pretty much anything". Political writer Howard Fineman has said that, "Biden is not an academic, he’s not a theoretical thinker, he’s a great street pol. He comes from a long line of working people in Scranton—auto salesmen, car dealers, people who know how to make a sale. He has that great Irish gift." Political columnist David Broder has viewed Biden as having grown since he came to Washington and since his failed 1988 presidential bid: "He responds to real people—that’s been consistent throughout. And his ability to understand himself and deal with other politicians has gotten much much better."


Final year
After ending his second presidential bid in January 2008, Biden focused instead on running for a seventh Senate term against Republican Christine O'Donnell. In late August 2008, he was picked by Obama to be his running mate. Biden nevertheless continued to run for Senate re-election as well as Vice President, as permitted by Delaware state law. On November 4, 2008, Biden was re-elected as senator, in addition to winning the vice presidency.

Having won both races, Biden made a point of holding off his resignation from the Senate so that he could be sworn in for his seventh term on January 6, 2009. He became the youngest senator ever to be sworn in for a seventh full term, and said, "In all my life, the greatest honor bestowed upon me has been serving the people of Delaware as their United States senator." Biden cast his last Senate vote on January 15, supporting the release of the second $350 million for the Troubled Assets Relief Program. Biden resigned from the Senate later that day; in emotional farewell remarks on the Senate floor, where he had spent most of his adult life, Biden said, "Every good thing I have seen happen here, every bold step taken in the 36-plus years I have been here, came not from the application of pressure by interest groups, but through the maturation of personal relationships."

Delaware's Democratic governor, Ruth Ann Minner, announced on November 24, 2008, that she would appoint Biden's longtime senior adviser Ted Kaufman to succeed Biden in the Senate. Kaufman said he would only serve two years, until Delaware's special senate election in 2010. Biden's son Beau is a possible candidate for the 2010 race, after ruling himself out of the selection process due to his serving with the Delaware Army National Guard in Iraq.