http://www.chicagotribune.com/news/nationworld/chi-071011obamaclinton,0,27913.story?coll=chi_tab01_layoutIt may be bye-bye Mr. Nice Guy for Democratic presidential candidate Barack Obama, who said Thursday that he is opening the "next phase" of his campaign and plans to more pointedly and aggressively go after frontrunner Sen. Hillary Clinton.
"Now is the time where we're going to be laying a very clear contrast between myself and Senator Clinton," the Illinois Democrat told CNN. "Not just on the past, not just on Iraq, but on moving forward."
Obama's campaign has focused heavily on his biography, and he has been criticized by some supporters for not more forcefully challenging the New York senator, who has a wide lead in national polls and in some early voting states.
A tired looking Obama, speaking from Chicago on a day off from the campaign trail, said he is not concerned about his polling numbers and does not expect them to change soon.