Even as he widens his lead in the 2012 presidential polls, Newt Gingrich spends substantial time on an activity that earlier, as a back-of-the-pack candidate, raised questions about his ultimate motive – selling and signing $25 copies of his books.

As his primary foe, Mitt Romney, and the White House intensify their efforts to negatively define Gingrich, his sole public event Friday is at a bookstore in Washington. On Saturday he flies to Des Moines, Iowa, for a televised Republican debate but plans to squeeze in an afternoon book signing.

Experienced campaign strategists cannot recall a top-tier contender devoting so much time to pitching products while seeking the White House. Romney, who also has a book out, has never sold it while stumping, his campaign said. President Barack Obama, a best-selling author in 2007 and 2008, did not incorporate sales events into campaign appearances, according to a spokesman for his re-election committee.

Gingrich's devotion to book sales, Republican strategists said, raises questions about the propriety of a candidate who is generating personal income while seeking the White House, as well as whether he is making the optimum use of limited campaign time.

Gingrich said that book sales, far from a distraction, effectively convey his views and values. They are "the cultural wing of what we're doing," he said in an interview. "I am a cultural teacher, with a political campaign to change a government. And that's how I see myself."

Gingrich, who now holds strong leads in the latest polls in Iowa, South Carolina and Florida, may be having the last laugh after a mutiny by staff members this spring who complained about his preference for pitching books and DVDs of movies he makes with his wife, Callista, over meeting with voters.

Callista Gingrich, also an author, sells an illustrated children's book, "Sweet Land of Liberty," about Ellis the Elephant, at campaign events. Although some buyers are under the impression that sales of their books, like T-shirts or coffee mugs, support the campaign, the proceeds go to the Gingriches personally, even as the campaign is scrambling to pay off debt and raise enough money to run an ambitious national campaign.

"People who are seriously considering someone for president of the United States, I'm not sure they see that the process should be financially beneficial to the candidate," said Jim Dyke, a former executive for the Republican National Committee.

"I don't know that it presents a presidential feeling to be there pushing your own book."

Steve Schmidt, who managed Sen. John McCain's 2008 presidential bid, said McCain never sold books while campaigning, but "we live in a new age," he said, one where Gingrich's sales efforts are consistent with how he leveraged his political capital to start businesses after quitting the House, consulting for nearly $2 million for Freddie Mac, for example.

"As Republican voters give consideration to a Gingrich nomination, one of the considerations is understanding what you're getting," Schmidt said. "He monetized his years of being speaker for consulting gains. Why wouldn't there be an expectation that he monetizes his front-running status?"

Campaign autobiographies have been fixtures since Jimmy Carter's "Why Not the Best?" introduced the little-known governor to a national audience. Nearly every Republican candidate this year has a book out, and at least two besides Gingrich – Herman Cain and Michele Bachmann – made bookstore appearances part of wooing voters.

Gingrich, who has written or co-written 24 works of nonfiction and historical novels, said there was nothing wrong with selling books while campaigning.

"I believe in free enterprise, and I think it's OK to make money," he said.

More than 100 buyers who lined up for his signature Saturday after a town hall-style appearance on Staten Island, N.Y., seemed to agree.

"I would support him with 40 bucks to come and watch him," said Adrienne Cusenza, a nurse, who had paid $40 for the Gingriches' two books. "I'm getting the books for nothing."

Campaign finance experts said that promoting a book for personal profit while running for office was within the law. The book signings are run by Gingrich Productions, of which Callista Gingrich is president, a company that produces and promotes the couple's books and documentary films. There is a prominent link to it from the campaign's website, and people can buy the full back catalog of Newt Gingrich's books, including historical novels about the American Revolution, the Civil War and World War II.

An experienced Republican consultant, Mark McKinnon, said he doubted voters perceived Gingrich as mercenary.

"On the contrary, I think voters view book-related events as just making the candidates more substantive," he said.

Gingrich's latest book, "The Battle of the Crater," is about black Union troops in the Civil War, which Gingrich said he would discuss and promote widely during Black History Month in February.

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