PBS journalist Gwen Ifill, moderator of tonight's vice presidential debate, dismissed conservative questions about her impartiality because she is writing a book that includes material on Barack Obama.

Ifill said Wednesday that she hasn't even written her chapter on Obama for the book, "The Breakthrough: Politics and Race in the Age of Obama," which is to be published on Jan. 20, the day a new president is inaugurated. She said Obama's story is only a small part of the book, which discusses how politics in the black community have changed since the civil rights era.

"I've got a pretty long track record covering politics and news, so I'm not particularly worried that one-day blog chatter is going to destroy my reputation," said Ifill. "... They can watch the debate ... and make their own decisions about whether or not I've done my job."

On Wednesday, columnist Michelle Malkin wrote in the New York Post about Ifill's book, saying "She's so far in the tank for the Democratic presidential candidate, her oxygen delivery line is running out."

Republican presidential nominee John McCain on Wednesday, however, spoke highly of Ifill: "I think Gwen Ifill is a professional and I think she will do a completely objective job because she is a highly respected professional."

Ifill questions why people assume her book will be favorable toward Obama. "Do you think they made the same assumptions about Lou Cannon [who is white] when he wrote his book about Reagan?" said Ifill. Asked whether racial motives were at play, she said, "I don't know what it is. I find it curious." ASSOCIATED PRESS