From NPR:

Election 2008
Examining Obama's 'Present' Votes in Illinois
by David Schaper

In Monday night's debate between Democratic presidential candidates, New York Sen. Hillary Clinton and former North Carolina Sen. John Edwards attacked Illinois Sen. Barack Obama's voting record from his days as an Illinois lawmaker.
"In the Illinois State Senate, Senator Obama voted 130 times 'present,'" Clinton said. "That's not 'yes.' That's not 'no.' That's 'maybe.'"
The actual number of Obama's "present" votes was 129 during his eight years in the Illinois Senate. Obama's campaign says anyone criticizing his "present" votes doesn't understand how this type of vote is used in the rough-and-tumble give-and-take of the Illinois legislature.
To register a vote in the Illinois General Assembly, lawmakers have a choice of three buttons on their desk. The "yes" button is green. The "no" button is red, and the "present" button is yellow, says Rich Miller, who writes and publishes The Capitol Fax, a daily newsletter and blog on Illinois politics.
"There's a saying in Springfield that there's a reason why the present button is yellow," Miller says.
But Miller says that not all "present" votes are cowardly, including those cast by then-state Sen. Obama.
"After having put some thought into it, I don't think that Barack Obama was necessarily a coward for voting present on those bills. In fact, I think he believed that he was doing the right thing, because something, in his mind, might have been unconstitutional," Miller says.
Miller points out that, at times, Obama was the only lawmaker voting "present" on bills winning near unanimous support, even on issues he supported and on one he sponsored.
Chris Mooney is a political science professor at the University of Illinois, Springfield.
"A person as cerebral as Sen. Obama might be prone to such a thing, thinking things through a little too carefully," Mooney says.
Mooney and other state capitol watchers and players say Illinois lawmakers often vote "present" as part of a larger party or issue bloc strategy.
Pam Sutherland is the president and CEO of the Illinois Planned Parenthood Council. She says Obama voted "present" at least seven times to provide cover to other abortion-rights supporters on such bills as the "Born Alive Infant Protection Act."
"Senators didn't want to vote pro-choice anymore, because they knew these were being used against them in their campaigns," Sutherland said.
Potentially more damaging for Obama is Clinton's attack about Tony Rezko, an indicted Chicago real estate developer and political fundraiser, whom Clinton characterized as a slumlord for whom Obama did legal work.
Billing records from Obama's former law firm show that he did do five hours of legal work in the late 1990s for community groups that partnered with Rezko's development company, but did not work for Rezko directly.
Still, the two have known each other since Rezko tried to recruit Obama out of law school for a job. Cindy Canary of the Illinois Campaign for Political Reform explains Rezko's place in Illinois politics.
"He's kind of been like a virus in our political culture, if you will, and he has given money to candidates on both sides of the aisle," she says.
When Obama bought a mansion in Chicago's Hyde Park neighborhood in 2004, Rezko's wife bought the lots next door and then sold a portion of it to Obama to expand his yard.
It happened at a time when Rezko was under federal investigation — for his fundraising activities on behalf of Illinois Gov. Rob Blagojevich, and his role on a couple of state boards and commissions.
Though there are no allegations of wrong-doing by Obama, Canary says the relationship may hurt him.
"I think this will stand out in Sen. Obama's career as the date he wishes he'd never gone on," she says.
Tony Rezko goes on trial Feb. 25, three weeks after much of the country votes in the Super Tuesday Democratic primaries.