The young, sandy-haired boy wears a self-satisfied expression. His small hand is clenched as if he is in the middle of a triumphant fist pump.

By now, Laney Griner is used to seeing the photo she took of her son in 2007 when he was 11 months old splashed across the Internet or featured in various advertisements. The child’s name is Sam, but for years the world has known him as the popular Internet meme, “Success Kid.”

Last week, Griner discovered her son’s copyrighted image in the last place she ever expected to find it: a campaign fundraising ad for Rep. Steve King (R-Iowa). King has repeatedly come under fire for inflammatory remarks and rebuked as racist, anti-Semitic or insulting to minorities. The ad superimposes Sam’s famous face over a blurred picture of the U.S. Capitol alongside all-caps text that reads, “FUND OUR MEMES!!!”

“I was filled with rage. It made me so angry,” the 44-year-old mother from Jacksonville, Fla., told The Washington Post on Monday. “It was just kind of shocking.”

Griner, who identifies as “really liberal,” said she never gave permission to King or his staff to use Sam’s likeness, and is working with her legal team to make sure they don’t continue. On Monday, Griner’s attorney sent a cease-and-desist letter, demanding the congressman and his campaign take down the meme from all platforms associated with them and acknowledge the misuse in a public apology, among other requests.

Stephen Rothschild, a lawyer for Griner, told The Post that as of late Monday, he had not received a response. The letter demands action by Wednesday. Otherwise, it says, Griner will sue King, his campaign and a conservative fundraising site that featured the ad for copyright infringement and violating Sam’s “personality rights.” King and his campaign did not respond to requests for comment.

“I don’t want anyone thinking I was willing to accept any amount of money for them to use it,” Griner said. “There’s no amount of money I would take for that. … We stay away from negative attachments, and this is about as negative as you can get in my mind.”

Griner first learned of the ad Thursday. A reporter from Media Matters for America, the liberal media watchdog group, tweeted a photo of the campaign’s Facebook page, which regularly posts memes disparaging Democrats and touting conservative talking points. The image showed a post linking to King’s WinRed page and asking for donations “to make sure the memes keep flowing and the Lefties stay triggered.”

The mother took to social media to distance her family from the ad, slamming King as a “vile man” and the Republicans as a “disgusting party.” By late Monday, the ad was still on WinRed, but the Facebook post appeared to have been taken down.

“When you look at Steve King’s Facebook, it’s just one super offensive post after another,” Griner told The Post.

The last thing Griner said she wanted was for her son, now 13, to be associated with “anything negative and so vitriolic,” noting the meme has largely been used in a positive context.

“It’s just the antithesis of what the meme’s reputation is,” she said.

“Success Kid” started as a funny picture of young Sam at the beach near his home in Jacksonville. Griner said she had just gotten a new camera and decided to take her son out for a seaside photo shoot. But as she snapped away, she realized Sam was more interested in stuffing sand in his mouth than posing.

The result? A photo of the boy staring straight into the camera, his lips pressed together with determination and a fistful of sand inches away from his face.

Shortly after Griner uploaded the picture to the photo-sharing website Flickr, the Internet went to work. The earliest attempts to meme Sam paired the child with the text, “I hate sand castles,” according to KnowYourMeme.com, a website that tracks viral Internet content. By 2011, Sam’s image was turned into what became its most popular form, dubbed “Success Kid” for its frequent use to describe “a situation that goes better than expected.”

Since Griner copyrighted the image in 2012, “stalwart American companies” such as Coca-Cola, General Mills and Microsoft have paid her to license it for advertisements, according to Monday’s letter. “Success Kid” was even used by President Barack Obama’s administration to promote immigration reform in 2013, after they obtained Griner’s permission.

“I’m a big supporter of Obama, so that was good for me,” she said.

In the letter, Griner’s attorney alleged King and his staff “falsely implied by your unauthorized use that ‘Success Kid’ is somehow associated with and supports your campaign” and “misrepresented to the general public that you are acting on behalf of and even have some proprietary interest in ‘Success Kid.’ ”

“The majority of U.S. consumers reject your political and other views, often vehemently, as they have a right to do,” the letter said. “Those people may be repelled by any association with your politics and campaign and, therefore, unwilling to purchase products from legitimate licensees of the ‘Success Kid’ meme.”

Griner stressed that politics was “a big part” of why she was upset with the campaign’s use of her photo. But she “wouldn’t be totally against” other Republicans using it, she said.

“It’s really about the message and the person who’s using it, who’s letting it be part of their brand,” she said. “Steve King is just not someone who should be using it. Hard to imagine any mother would want their child to be associated with that.”