Legislative career: State Senator: 1997–2004

Obama was elected to the Illinois Senate in 1996, succeeding State Senator Alice Palmer as Senator from Illinois's 13th District, which at that time spanned Chicago South Side neighborhoods from Hyde Park – Kenwood south to South Shore and west to Chicago Lawn.

Legislative career: U.S. Senate campaign

In May 2002, Obama commissioned a poll to assess his prospects in a 2004 U.S. Senate race; he created a campaign committee, began raising funds and lined up political media consultant David Axelrod by August 2002, and formally announced his candidacy in January 2003.

Legislative career: U.S. Senator: 2005–2008

Obama was sworn in as a senator on January 4, 2005, at which time he became the only Senate member of the Congressional Black Caucus.

CQ Weekly characterized him as a "loyal Democrat" based on analysis of all Senate votes in 2005–2007. The National Journal ranked him among the "most liberal" senators during 2005 through 2007 (the ranking has been criticized by liberal groups such as Media Matters for America).

He enjoyed high popularity as senator with a 72% approval in Illinois. Obama announced on November 13, 2008 that he would resign his Senate seat on November 16, 2008, before the start of the lame-duck session, to focus on his transition period for the presidency.