From the article:
Durbin, a former parliamentarian for the Illinois State Senate, said the Clinton allies were not familiar with how things worked in Illinois. "Voting present was a widely accepted legislative strategy used to champion progressive causes, or to ward off legislation that was unfinished or unconstitutional," Durbin said in a statement issued by the Obama campaign.
A front-page story in the Thursday New York Times detailing Obama's "present" voting history triggered the renewed attack. Earlier this month, Clinton said, "A president can't vote 'present.' A president can't pick and choose which challenges he or she will face," focusing on nine roll calls where Obama voted "present" on abortion and gun-control measures.