Bo, the Portuguese water dog who became the President’s first pet to riot in the Halls of Power at the Obama White House, died on Saturday.

Bo, who was 12 years old, had cancer, Michelle Obama said on Instagram. President Barack Obama said the family has lost “a true friend and companion”.

“Bo has been a constant, gentle presence in our lives for over a decade – happy to see us on our good days, our bad days, and every day in between,” wrote Obama on Twitter.

“He tolerated all the excitement of staying at the White House, had a big bark but no bite, liked to jump into the pool in summer, was unwavering with kids, lived for junk at the dining table, and had great hair. ”

Bo arrived at the White House in April 2009 as a 6-month-old puppy, a gift from Massachusetts Senator Edward M. Kennedy and his wife Victoria to their first children Malia and Sasha Obama.

The girls named the dog Bo because their cousins ​​had a cat of the same name and because Mrs. Obama’s father was nicknamed Diddley after the musician Bo Diddley.

The dog was an instant object of national fascination, the youngest in a long line of four-footed White House residents that included the Beagles of President Lyndon B. Johnson, him and her, the King Charles Spaniel of President Ronald Reagan, Rex and that of President Bill Clinton included Cat, Socks, and President George W. Bush’s Scottish Terrier Barney.

President Biden resumed the tradition with his two German Shepherds, Champ and Major, in January after President Donald J. Trump’s tenure ended as the first in decades without pets living in the residence. Major was recently sent off for training after a series of biting episodes.

Bo was known to frolic outside the White House press corps on South Lawn, barking at press conferences, and attracting fan mail from children across the country.

He also posed with his tongue out for an official White House portrait and was the subject of a children’s book, Bo, America’s Commander on a Leash, written by Naren Aryal and illustrated by Danny Moore.

In 2013, Bo was joined by a second Portuguese water dog, Sunny, at the White House after Ms. Obama said Bo needed more interaction with other dogs.

Ms. Obama said, although Bo was originally intended to be a companion for Malia and Sasha, “We had no idea how much he would mean to all of us.”

She said the dog had been a “constant comforting presence in our lives” and strolled into her offices “as if he owned the place, a ball clamped in his teeth.”

He was there for the traditional Easter egg roll on the South Lawn and when the Pope came to visit she said.

After Malia and Sasha went to college, Bo helped the couple get used to life as empty nests, said Ms. Obama in a post on Instagram signed “Michelle, Barack, Malia, Sasha and Sunny”.

“Last year, no one was happier than Bo when everyone was home during the pandemic,” she wrote. “All his people were under one roof again – just like the day we got him.”