A new wave of criticism about Obama's connections to Rezko came last week in response to Obama's attempts to link McCain to former Christian Coalition leader Ralph Reed. Obama also mocked McCain for not being able to answer a reporter's question last week about how many houses he owns.
The McCain campaign has chosen not to go on the defensive over that political fumble but instead hit Obama on the subject of homes.
"When Barack Obama used financial backing from a corrupt political contributor to buy his family a million-dollar mansion that he couldn't afford, it raised questions," said McCain campaign spokesman Tucker Bounds.
Rezko is a longtime friend of and political donor to Obama. In 2005, Rezko's wife purchased land next door to Obama's on the same day the presumed Democratic nominee closed on his $1.6 million home. A few months later, Rezko's wife sold the Obamas a 10-foot-wide strip of their land adjacent to the home. At the time, Rezko was already under investigation by federal authorities.
In June, Rezko, also an adviser and fundraiser to Illinois Gov. Rod Blagojevich, was convicted of taking money in exchange for obtaining favors for clients doing business with the state.
McCain advisers said they would not have gone after Obama over the Rezko matter had Obama not gone after McCain over Reed and McCain's homes.
A recent Obama campaign ad suggested McCain was too cozy wtih "Republican power broker" Ralph Reed who has been linked to the scandal involving lobbyist Jack Abramoff, who is now serving time in federal prison and was the target of a probe by the Senate committee McCain chaired.
Reed sent an e-mail to potential donors about a recent McCain fundraiser in Georgia.
The Democrats' ad states, "And who's now raising money for McCain's campaign? Ralph Reed."
Former Radical Activist Turned Chicago Professor
The McCain campaign also attacked Obama Monday over ties to Ayers, a former radical activist who admitted bombing government buildings in the 1960s when he was a part of the the Weather Underground, an anti-war group. Ayers is now a professor of education at the University of Illinois at Chicago.
A conservative group, American Issues Project, has been running television ads in Ohio and Michigan questioning Obama's ties to Ayers. Some members of the American Issues Project are McCain fundraisers, but it is not formally connected to the McCain campaign.
The Obama campaign also did not take the attacks lying down. It issued its own response ad that said in part, "With all our problems, why is John McCain talking about the '60s, trying to link Barack Obama to radical Bill Ayers?"
In fact, the McCain campaign had not itself mentioned the Ayers connection since April, when McCain raised questions about Obama's relationship to an "unrepentant terrorist." But once the Obama ad ran, the McCain campaign fired back.
"[Obama] understates his relationship with [Ayers]," said Steve Schmidt, a top adviser to McCain. "He does have a relationship which is deeper than what he's previously said about it. It's a fair issue to discuss."
But just how close were Obama and Ayers? Obama insists that he barely knows Ayers or his wife, Bernardine Dohrn, who is now a professor at Northwestern University's School of Law . Dohrn was also a member of the Weather Underground, and was once on the FBI's Top 10 Most Wanted List for inciting to riot. The couple live in Chicago and have long been politically active there.
In the early 1990s, Obama attended a fundraiser for his state senate campaign at the couple's home in the same Hyde Park neighborhood where he lives. Ayers once donated $200 to an Obama campaign for the state legislature. Obama and Ayers also served together on the board of the Woods Fund, a charity that develops community organizations to serve the poor. Ayers founded the Chicago Annenberg Challenge, a school reform group, that Obama chaired from 1995 to 1999.
The University of Illinois at Chicago on Tuesday released thousands of pages of documents detailing the activities of the Annenberg Challenge. A partial review of those documents by ABC News found few details of their work together and little evidence that Obama and Ayers were particularly close.
"The notion that & me knowing somebody who engaged in detestable acts 40 years ago, when I was 8 years old, somehow reflects on me and my values doesn't make much sense," Obama said when he was asked about Ayers during the Democratic debate in Philadelphia last April.
An Obama campaign spokesman was also quoted in USA Today saying, "The last time Obama saw Ayers was about a year ago when he crossed paths with him while biking in the neighborhood. The suggestion that Ayers was a political adviser to Obama or someone who shaped his political views is patently false."
Ayers admitted planting bombs at a number of government installations in the 1960s as part of protests against the Vietnam War, but he was never convicted for any crime related to these activities and no one was hurt in the incidents. In a New York Times article that, coincidentally, happened to be published Sept. 11, 2001, Ayers said "I don't regret setting bombs. I feel we didn't do enough."
McCain campaign spokesman Brian Rogers hit hard on the Ayers issue Monday.
"The fact that Barack Obama chose to launch his political career at the home of an unrepentant terrorist raises more questions about Sen. Obama's judgment than any TV ad ever could," Rogers said. "And the fact that he's launching his own convention by defending his long association with a man who says he didn't bomb enough U.S. targets tells us more about Barack Obama than any of tonight's speeches will."
Controversial Pastor Jeremiah Wright
On another offensive, the McCain campaign also signaled that it may revive the issue of Obama's relationship with his former pastor, the Rev. Jeremiah Wright, a topic that caused a wave of criticism and negative media attention during the Democratic primary battle last spring.
At the time, McCain said he would not criticize Obama over Wright's remarks.
Obama dissociated himself from Wright last spring and formally left Wright's church after media reports about some of Wright's more controversial sermons and positions. Those included remarks that 9/11 was "chickens coming home to roost" and that America should be punished by God for its racist history.
On Monday, Schmidt said he would not rule out Wright becoming an issue in the fall campaign.
Mark Halperin, Time magazine political analyst and an ABC News consultant, predicts that one way or another, Wright will likely be brought up again in the election campaign.
"Even if John McCain and his campaign don't directly raise Rev. Wright, I suspect before this is over, given how tight this race is, that you'll have allies of McCain in advertising trying to help define Barack Obama in negative terms linked to Jeremiah Wright. That is the danger the Obama campaign is well aware of."
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