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WASHINGTON— President Obama called Vice President Biden "one of the best vice presidents in our history" on Thursday, just days after a newly published book revealed that the White House had done polling on swapping Biden for Hillary Rodham Clinton for his reelection bid.

In an interview with Chuck Todd of NBC News, Obama left some wiggle room as to whether he knew that his aides—as reported in Double Down: Game Change 2012—explored the possibility of the swap.

Adding Clinton to the ticket, however, didn't materially improve Obama's odds and the idea of a swap was scrapped, the authors Mark Halperin and John Heilemann write.

Asked about the book's revelation, the president didn't deny that idea was explored.

"I am in charge of two million people in the federal government," Obama said. "So people do all kinds of stuff. Some of it-- they clear with me, sometimes they're trying to figure something out-- particularly on the political side. And I'm not somebody who delves into polling and-- all that data."

He added: "Here's the one thing I can say for certain. That if they had asked me, I would have said there is no way that I'm not running again with Joe Biden."

Obama went on to call Biden a friend and one of his most important policy advisers.

"When my back's up against the wall, he has my back," Obama said.