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 book store 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-selling, 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 conveyed 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 book-store 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."

Kenneth May, a technician for an oil refinery in New Jersey, held three copies of Gingrich’s book that he planned to share with friends.

"I’m helping his campaign as far as I’m concerned," he said. "Plus it helps me to learn more about him."

The operation was smooth and efficient. An aide asked each customer’s name, wrote it on a Post-it note on the title page and slid it over to Callista Gingrich. She inscribed the book with the buyer’s name before sliding it to her husband.

Newt Gingrich, wielding a blue Sharpie and sipping a Diet Coke, scrawled his name and shook the buyer’s hand. He rarely spoke before turning to the next customer.

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.

"It has a lot of different signals to a lot of different people that there are things in American history worth knowing," he said. "You have to see me as a teacher."

When Gingrich was an also-ran candidate earlier in the year, there was speculation that he was mainly seeking to raise his value as an author and a paid television commentator. Observers pointed to the model of Mike Huckabee, who won the 2008 Iowa caucuses, dropped out of the race soon after but ended up with his own show on Fox News.

"Pat Buchanan perfected this process years ago," said Rick Tyler, a former longtime aide to Gingrich. "Pat would go run for president and then get a better contract with CNN. Others picked up on it."

Tyler, a co-writer with Gingrich, said, "We worked for years restoring Newt’s brand because it was damaged once he left the speakership." In 2008, they had a New York Times best-seller with the nonfiction book "Real Change."

But when "A Nation Like No Other" was released in June, just as Gingrich’s campaign was imploding, it flopped.

Now things are different. "A Nation Like No Other" has sold 15,000 hardcover copies, according to Nielsen BookScan, and the Kindle e-book edition is No. 64 among political books.

"The behaviors of someone running for president and someone trying to gain market viability are exactly the same," Tyler said. "You can’t tell them apart."

© 2011 The New York Times Company