Now that Herman Cain has launched a bestseller with his brand new book This is Herman Cain! the Republican candidate for president says he will shift away from a focus on book sales and promotion last week to better focus on his campaign, and key early voting states like New Hampshire and Iowa in particular.

Last week Cain launched a tour for his new book, This is Herman Cain! My Journey to the White House, published by Threshold Editions (an imprint of Simon and Schuster). That focus was apparently beneficial, in terms of book sales, as initial sales figures on Wednesday from Nielsen Bookscan, which tracks national book sales, show that Cain's memoir was among last week's national bestsellers.

Among new hardcover books, This is Herman Cain! was sixth in national sales last week, according to Bookscan, with 12,533 books sold in the U.S. Bookscan accounts for 80 percent or more of all books sold in the U.S., including Amazon, Barnes & Noble and many independent book stores.

Cain's book is sold out of inventory at Ingram, a large industry wholesaler, and it is also sold out in hardcover at Amazon, with delivery within 7 to 10 days. Cain's book is currently ranked number 19 at Amazon among its bestsellers, but the number has likely dropped slightly since Amazon is out of stock.

Launching as the number 6 bestselling new hardcover according to Bookscan makes Cain's book almost a certainty for upcoming leading industry bestseller lists, including the New York Times.

But while Cain promoted his book launch last week, some critics thought he was spending more time trying to profit from his recent fame and surge in most polls to the top of contenders for the Republican party's presidential nomination. On Wednesday, however, as Cain's book sold out of stock and was poised to make bestseller lists, he said he was is going to focus on the campaign.

The book tour is over, Cain said, speaking with reporters near the New Hampshire State House Wednesday afternoon.

Cain said he will campaign more aggressively, adding staff and spending more money in a focus on key states including New Hampshire and Iowa.

We have run this (campaign) very lean by design, said Cain, according to The Associated Press. We are now going to ramp up. We now have the money to do so. I didn't want to get out in front and commit to spending a whole lot of money before I knew that the American people were going to say, 'You know what? This long shot may not be such a long shot.'

The former Godfather's Pizza CEO has never held elected office after one previous run for president and another previous for a Georgia Senate seat but after winning the Florida straw poll last month he's rocketed past Texas governor Rick Perry in most polls. He's still trailing front-runner Mitt Romney in most, however.

Cain has been criticized for putting little effort into spending time and money in they key early voting states. But he pledged on Wednesday that is about to change.

It may not be possible to overcome (Romney's) big lead, but it is possible to close that gap, Cain said.