The Donald is back. After squashing rumors in May that he would run for president, real estate mogul Donald Trump has re-emerged on the political radar, announcing plans to moderate a Republican presidential debate , endorse a GOP candidate and, again, floating the possibility that he would relaunch a presidential bid.

Coincidentally, the billionaire businessman is popping back onto the political scene at the same time that his new book is dropping onto bookshelves, causing some to question if he is more interested in presidential politics or book sales.

"It's a head fake," University of Iowa political science professor Timothy Hagle said of Trump's talk to run for president as an independent. "Donald Trump is a promoter, and he's largely a promoter of Donald Trump."

"I don't mean that disparagingly," Hagle said. "Candidates have to do this too. You have to have a brand. Donald Trump is a brand and a very successful brand."

Trump's tactic , whether it is intentional or coincidental, is tried and true. Authors-turned-presidential candidates have seen their book sales soar as they rise in the polls.

Take President Obama, for example. In 2006, before he broke out on the national scene as a presidential possibility, then-Sen. Obama pulled in less than $1 million in profits from his two books, according to the tax return his campaign released.

A year later, when his presidential campaign was in full swing, Obama's reported income jumped to $4.2 million, almost all of which was from a spike in book sales.

Three of the 2012 GOP candidates have devoted a chunk of their campaign time to selling books, and, in the case of now-front-runner Newt Gingrich, documentary movies.

Both Herman Cain, who suspended his campaign Saturday, and Michele Bachmann have released books over the past two months. They have each conducted at least 10 book signings.

Since September Gingrich, along with his wife, Callista, has hosted 11 movie screenings for the couple's three documentary films and 10 book signings, one of which, in Naples, Fla.,  sold more than 600 books, according to a report  in the Naples News.

"It almost feels like these runs for president are just publicity stunts," said Barbara Perry, a senior fellow at the University of Virginia's Miller Center. "They are just using these books as a springboard to fame and fortune, including using these books to run for the highest office in the land."

In June, when the top echelon of his campaign quit en masse , Gingrich's insistence on promoting his products as well as his campaign was one reason the strategists decided to call it quits.

Gingrich's campaign insisted the books and movies were  just another way to get his message to voters.

"The movies and books are part of a larger argument about the direction of the country that he's been making for over decade," Gingrich's spokesman R.C. Hammond told Politico in July. "He sees them as important communication devices - what his values are, what's wrong with the country and what he thinks can be done about it."

Book tours can be a good way for potential candidates to "test the waters," Hagle said, but at this point in the campaign, with the Iowa caucus less than a month away "it just doesn't seem reasonable."

Gingrich plans to take a break from campaigning in early primary and caucus states next week for a book signing with his wife in Washington, D.C., on Friday.

"When he is out on the stump now it is a branding experience for him to sell books and dvds," Perry said. "But since he is also interested in the presidency, it is also campaigning."

Perry credited Sarah Palin for blazing the trail on how to turn a presidential bid into a "monetary win." Since the former Alaska governor was tapped as John McCain's vice presidential running mate in 2008, she has signed two book deals, created a reality TV show and earned millions from speaker fees.

"I think that's what drew Herman Cain into this," Perry said, of Cain's now-defunct bid for the Republican nomination. "He probably saw it as an opportunity to get his name out there, do a book tour and have it coincide with presidential run."

Columnist George Will agreed, telling ABC's Christiane Amanpour that Cain was an "entrepreneurial charlatan." On ABC's This Week, Will said Cain used his campaign "as a book tour in a fundamentally disrespectful approach to the selection of presidents."

But Dan Logan, president of the Boston-based advertising firm Trinity Marketing, said building a brand is what political campaigns are all about, and writing a book is part of boosting that brand recognition.

"It's part of the American political scene and within the boundaries of you how you play the game," Logan said, adding that the "frustrating and disappointing" part of politics is that some candidates are "in it for their own gain as opposed to the good of the country."