Joseph Isadore "Joe" Lieberman (born February 24, 1942) is the junior (Seniority in the United States Senate) United States Senator (United States Senate) from Connecticut. First elected to the Senate in 1988, Lieberman was elected to a fourth term (United States Senate elections, 2006) on November 7, 2006. In the 2000 United States presidential election (United States presidential election, 2000), Lieberman was the Democratic (Democratic Party (United States)) nominee for Vice President (Vice President of the United States), running with presidential (President of the United States) nominee Al Gore, becoming the first Jewish candidate on a major (major party) American political party presidential ticket. The Gore–Lieberman ticket won the popular vote but ultimately failed to gain the electoral votes (electoral college) needed to win the controversial election. Lieberman ran for re-election to the U.S. Senate while he was also Gores running mate, and he was re-elected by the voters of Connecticut. He was an unsuccessful candidate for the Democratic presidential nomination in the 2004 presidential election (United States presidential election, 2004).

During his re-election bid in 2006, he lost the Democratic Party primary election (Democratic Party primary, Connecticut United States Senate election, 2006) but won re-election in the general election as a third party (Third party (politics)) candidate under the party label "Connecticut for Lieberman." Lieberman has been officially listed in Senate records for the 110th (110th United States Congress) and 111th Congresses (111th United States Congress) as an "Independent Democrat" and sits as part of the Senate Democratic Caucus. But since his speech at the 2008 Republican National Convention (2008 Republican National Convention#Tuesday, September 2, 2008) in which he endorsed John McCain for president, Lieberman no longer attends Democratic Caucus leadership strategy meetings or policy lunches. On November 5, 2008, Lieberman met with Senate Majority Leader Harry Reid to discuss his future role with the Democratic Party. Ultimately, the Senate Democratic Caucus voted to allow Lieberman to keep chairmanship of the Senate Committee on Homeland Security and Governmental Affairs. Subsequently, Lieberman announced that he will continue to caucus with the Democrats.

Lieberman remains a registered Democrat. He was one of the Senates strongest advocates for continued prosecution of the war in Iraq (Iraq War). He is also an outspoken supporter of the U.S.-Israel relationship. On domestic issues, he strongly supports free trade economics while reliably voting for pro-trade union legislation. He has also opposed filibustering Republican judicial appointments. With Lynne Cheney and others, Lieberman co-founded American Council of Trustees and Alumni in 1995. Lieberman is a supporter of abortion rights and the rights of gays and lesbians (LGBT rights) to adopt children (gay adoption) and be protected with hate crime legislation (Hate crime#Hate crime laws). Lieberman is one of the Senates leading opponents of violence in video games and on television. Lieberman describes himself as being "genuinely an Independent," saying "I agree more often than not with Democrats on domestic policy. I agree more often than not with Republicans on foreign (foreign policy) and defense policy (defense (military))."

Liebermans approval rating in a poll taken January 4-5, 2010, was 25% approve versus 67% who disapprove, making him one of the least popular Senators currently in office.