Sen. Joe Biden on Tuesday told reporters camped outside his Delaware home that it's not him.
"You got better things to do guys; I'm not the guy," he said.
Asked where he would be on Saturday -- when Obama is reportedly scheduled to hold a campaign event in Springfield, Illinois, that may feature his new running mate -- Biden replied, "Here," pointing to his driveway.
He softened up a little later that night, telling reporters, "I promise you, I don't know anything."
Along with Biden, Sen. Evan Bayh of Indiana and Virginia Gov. Tim Kaine are considered to be among the top tier of VP contenders.