Let us take a good look at these questionable associations:
GOV. ROD BLAGOJEVICH: Obama has maintained a cordial but distant relationship with Blagojevich during the governor's tenure.
He has complimented Blagojevich for running "a sound administration" with "the right priorities." He supported his fellow Democrat for re-election in 2006, even though the governor backed someone else over Obama in the U.S. Senate Democratic primary.
Obama's circle of major Illinois political allies and supporters is largely separate from Blagojevich's, with two major exceptions. Both Obama and Blagojevich got extensive money and support from Chicago businessman Antoin "Tony" Rezko. At least one top aide to Obama, Michael Strautmanis, previously worked for Blagojevich.
But Blagojevich's disdain for Obama was clear in court documents released Tuesday after the Illinois governor was arrested. Blagojevich, accused by federal prosecutors of conspiring to sell or trade for personal benefits the Senate seat left vacant by Obama, was overheard complaining at one point that Obama's people are "not going to give me anything except appreciation." He added: "(Expletive) them."
Obama said Tuesday, "I had no contact with the governor or his office, and so I was not aware of what was happening."
ANTOIN REZKO: "Tony" Rezko, who raised money for the campaigns of both Obama and Blagojevich, is awaiting sentencing after being convicted in June on charges of using clout with Blagojevich's administration to help launch a $7 million kickback scheme.
The charges have no connection to Obama, but Rezko is tied to the Illinois senator in other ways.
Rezko and his family donated at least $21,457 to Obama and helped raise over $200,000 more, though not for his presidential bid. He also advised Obama on the purchase of a new Chicago home and, in his wife's name, purchased a vacant lot next door to the new Obama home when the seller wanted to dispose of both properties at the same time. Rezko then sold a slice of the property to Obama.
Obama has donated Rezko's contributions to charity and says it was a mistake to work with Rezko on buying the house.
JEREMIAH WRIGHT: Wright was Obama's minister for 20 years. He helped Obama embrace Christianity, performed Obama's marriage, and baptized Obama and his two daughters.
Wright was known for thundering "God Damn America" in clips that dominated cable television news programs for weeks last spring. Wright accused the government of creating AIDS.
Obama has done his best to distance himself from his former minister, to the point of resigning from the church that Wright once led.
Wright's comments were a stumbling block for Obama's campaign. In an impassioned speech about faith and race, the Democrat at first expressed support for Wright, saying that "I can no more disown him than I can my white grandmother."
But six weeks later during a speech at the National Press Club, Wright offered eyebrow-raising opinions about the U.S. government, praised Nation of Islam leader Louis Farrakhan and hinted that Obama was distancing himself from the pastor for political expediency.
The next day, Obama said he was outraged and denounced Wright's remarks.
WILLIAM AYERS: Today, Ayers is a university professor and a member of Chicago's intellectual establishment. Forty years ago he was a member of the Weather Underground, a radical group that claimed responsibility for a series of bombings, including nonfatal explosions at the Pentagon and U.S. Capitol.
Ayers was a fugitive for years with his wife, fellow radical Bernadine Dohrn. But after surrendering in 1980, the charges against Ayers were dropped because of prosecutorial misconduct.
Obama had a very limited relationship with Ayers, who lives in the same neighborhood. They served together on the board of a Chicago charity, and in the mid-1990s when Obama first ran for office; Ayers hosted a meet-the-candidate session for Obama at his home.
Ayers was front and center in GOP claims that Obama was "palling around with terrorists," as Republican vice presidential nominee Sarah Palin put it.
Obama has condemned Ayers' radical activities, and there's no evidence they ever were close friends or that Ayers advised Obama on policy.
Ayers said in November that he hardly knew Obama. "I think my relationship with Obama was probably like thousands of others in Chicago. And, like millions and millions of others, I wish I knew him better," Ayers said in a newspaper interview.
EMIL JONES: Jones, the president of the Illinois Senate, amounts to Obama's political godfather and was an important part of Obama's long shot victory for U.S. Senate in 2004. He helped the little-known politician meet the right people, and he picked Obama to handle high-profile legislation during the two years leading up to the election.
But Jones' political style is very different from Obama's.
Jones is known for steering state money to a few favored institutions, including some that employ his relatives. Several of his relatives have gotten state jobs, and his wife's government salary jumped 60 percent after he became Senate president. He has played an important role in blocking ethics legislation in Illinois.
When Jones announced last summer that he would retire from the Illinois Senate when his term ends in January, an Obama campaign spokesman said "Jones has been a passionate advocate who has fought for working families and the underprivileged."
Jones was considered a possible successor to Obama in the Senate.
RASHID KHALIDI: Khalidi is a scholar and author on Middle Eastern affairs who has criticized Israeli policies and was part of a Palestinian advisory panel to peace talks in the early 1990s.
He's also a friend of Obama.
They met while both were teaching at the University of Chicago and living in the same neighborhood. Obama and his wife, Michelle, sometimes had dinner with Khalidi and his wife, Mona. The Khalidis hosted a political fundraiser for Obama in 2000, and the Woods Fund charity gave money to the Arab-American Action Network, run by Mona Khalidi, while Obama served on the charity's board.
Khalidi and Obama have both said they hold very different opinions on Israeli issues, but their friendship has been used to raise questions about Obama's support for Israel — and to generate Internet headlines such as "Meet Obama's Terrorist Friend."
Late in the 2008 presidential campaign, the Republican nominee, John McCain, and Palin criticized Obama for attending a 2003 party for Khalidi. Obama's campaign dismissed the complaints, saying Khalidi was not an adviser to him and that Obama does not share Khalidi's views.
MICHAEL PFLEGER: Pfleger, a Roman Catholic priest in Chicago, has been known as a firebrand for years. He has protested over a wide range of issues, including gun shops and Jerry Springer. Obama has referred to him as a spiritual adviser.
Last spring, Pfleger visited Obama's church and preached a sermon in which he mocked Hillary Rodham Clinton and accused her of expecting to win the presidential nomination because she was white. Pfleger apologized, but Obama condemned the remarks and resigned from the church.