ABC News' Amy Bingham and Elicia Dover report:

On the day before a pivotal Republican presidential debate in Iowa, shortly after national polls solidified him as the GOP front-runner and amid criticism that his campaign organization in Iowa is skeletal at best, Newt Gingrich decided to make his only public appearance today 1,000 miles away from the first-in-the-nation caucus state.

Gingrich and his wife, Callista, had planned to spend the afternoon selling and signing their books at Washington, D.C.'s Union Station, but cancelled at the last minute after citing public safety concerns. The bookstore, it seems, could not handle the crowd.

Hudson News spokeswoman Laura Samuels said the security plan for the signing was set up in October when the Gingrichs originally agreed to the event.

"In the interim time his camp has really taken way off," Samuels said. "We reviewed the plan for crowd control and just said 'Nah, this is going to be too many more people than we originally intended.'"

Gingrich campaign officials will instead host a conference call contrasting his positive messaging with rival Mitt Romney's negative advertising.

This morning, both The New York Times and The Washington Post ran stories about how Newt Gingrich continues to hold book signings while campaigning-a point ABC made earlier this week. The Times headline today is "Gingrich, Ahead in Polls, Is Still Selling Books" and the Post ran a story with the headline "Gingrich book-selling efforts test sprit of campaign laws." Read HERE and HERE .

Since September Gingrich and his wife have held 10 book signings for their three books and 11 screenings of their three documentary films.

In July, shortly after 16 of his top campaign advisers quit, Gingrich's campaign spokesman R.C. Hammond told Politico that the product promotions are part of his campaign strategy.

"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," Hammond said.

The disavowed staffers quit, in part, because of Gingrich's insistence on holding the book and movie events, often in states that are not traditionally part of the primary campaign trial. Before leaving the campaign, a senior staffer even emailed the team saying "we didn't sign up to be hucksters for products for sale."

That was long before Gingrich's rise to the top of the primary pack.

ABC's Elicia Dover