"Triggered" is a New York Times best seller, but a dagger next to its listing raises questions. Willy Kurniawan/Reuters

Donald Trump Jr.'s book "Triggered" has topped the New York Times best-seller list, but a small dagger symbol next to the listing raised suspicions that it might be at the top of the pile because of bulk orders.

The dagger symbol, (†), is used to indicate when a title is linked to "Institutional, special interest, group, or bulk purchases," according to The New York Times.

A tweet posted on November 5 shows an email from Trump in which signed copies of "Triggered" were offered by the Republican National Committee to anyone making a donation of $50 or more.

President Donald Trump, who expressed pride in his son's best-seller status in a tweet Thursday, was previously criticized for using his platform to promote the book.

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Donald Trump Jr.'s new book, "Triggered: How the Left Thrives on Hate and Wants to Silence Us," is No. 1 on the New York Times best-seller list, but it may be due to bulk buying linked to the Republican Party.

The book came out last week and is marketed in the book's Amazon listing as partially a memoir and partially an exposé on the "tricks that the left uses to smear conservatives and push them out of the public square."

The New York Times best-seller list as released Thursday featured the book as No. 1 in nonfiction - but a small dagger symbol appears next to the listing.

The dagger symbol, (†), is used to indicate when a title is linked to "Institutional, special interest, group, or bulk purchases," according to The New York Times.

The Times' website says such titles are included on the best-seller list at the discretion of the editors and "when included, such bulk purchases appear with a dagger (†)."

"It's known in the industry as the 'deadly dagger,'" a source told the celebrity news site Page Six. "A rare penalty that is only called for flagrant fouls."

A tweet from the White House reporter Zeke Miller posted on November 5 showed an email from Trump in which signed copies of "Triggered" were offered by the Republican National Committee to anyone making a donation of $50 or more.

Steve Guest, a Republican National Committee spokesman, confirmed to the Associated Press that the committee had been offering the book as part of a fundraising campaign.

He said copies were bought "to keep up with demand" and not in a "large bulk purchase," according to the AP.

President Donald Trump expressed pride in a tweet Thursday with his son's book becoming a best seller.

He was, however, previously criticized as using his platform to promote the book, tweeting on November 4 to implore his followers to order the book.

Liz Hempowicz, the director of public policy at the Project on Government Oversight, a nonpartisan government watchdog group, told the AP that the tweet was "a misuse of public office and it would be an official misuse of public policy if it was anyone other than the president."

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