Democratic presidential candidate Sen. Barack Obama, D-Ill., shakes hands with Honolulu Mayor Mufi Hannemann at the airport Friday before boarding a plane to leave Honolulu after vacationing in Hawaii. The Obama campaign has created a 41-page refutation to author Jerome Corsi's book, Obama

Washington ? It makes sense for Sen. Barack Obama to slug it out with Jerome Corsi, whose new book paints the presumptive Democratic nominee as a dangerous radical, analysts said Friday.

But Obama’s strategy also carries some risks.

“The old saying is that when you get in the gutter, everybody gets dirty,” said Kevin Wagner, an assistant professor of political science at Florida Atlantic University, particularly with information flying across the Internet.

Corsi’s book, “Obama Nation: Leftist Politics and the Cult of Personality,” is No. 1 on The New York Times hardcover nonfiction bestseller list.

The Obama camp responded Thursday with a 41-page, point-by-point refutation of the key charges.

Corsi is well-known in political circles. Four years ago, he co-wrote with John O’Neill, co-founder of Swift Boat Veterans for Truth, the book “Unfit for Command,” which raised questions about Democratic presidential nominee John Kerry’s military record.

Corsi, who earned a Ph.D. from Harvard University in political science, has said he plans to vote this year for Chuck Baldwin, the Constitution Party’s presidential candidate.

He argues in his book that Obama’s election would mean “a repeat of the failed extremist policies” that have dominated the Democratic Party for years.

To critics, such arguments are reminiscent of Corsi’s 2004 assertions about Kerry, a decorated Vietnam veteran.

The senator responded to charges in the book and by the Swift Boat Veterans for Truth, but his reply was widely criticized as being too academic and low-key.

Obama’s camp tried to show that it had learned that lesson this week with its lengthy refutation, which it called “Unfit for Publication.”

Perhaps just as significantly, spokesman Tommy Vietor slammed Corsi, calling him “a discredited liar who is peddling another piece of garbage in order to continue the Bush-Cheney politics he helped perpetuate four years ago.”

Corsi explained this week on CNN that “the book is designed to say that I oppose the candidacy of Barack Obama, and I explain why.”

Corsi couldn’t be reached for comment Friday.

Berkovitz said there generally were two ways to respond to such charges.

One method, used by Kerry and in 1988 by Democratic nominee Michael Dukakis, is to take a higher road.

The other way to confront what seem like wild allegations, credited most recently to Bill Clinton in the 1990s, is to respond early, fiercely and often.

The problem with such aggressive responses is that they risk keeping the story alive.

“Reminding people of negative information isn’t usually helpful. You can give credibility to it even though you’re saying it’s wrong,” said Susan Sterett, a professor of political science at the University of Denver.