Presidential hopeful Hillary Clinton tells PEOPLE that Charlotte called her grandma for the first time at the first Democratic debate of the 2016 presidential race

The first Democratic debate of the 2016 presidential race was a big night for Hillary Clinton. And its significance didn’t go unnoticed by her granddaughter, Charlotte.

The night marked the first time the 1-year-old called Clinton “grandma.”

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“It was pretty exciting,” Clinton tells PEOPLE. “We’re going to let her decide if she wants to stick with that.”

The presidential hopeful recently took a quick campaign detour to do some Christmas shopping and bought a knit hat for her granddaughter.

Charlotte was bound to utter the magic word sooner or later, as Chelsea Clinton recently described her mother as a devoted babysitter to her own daughter, who turned 1 in September.

And Chelsea said her mother does it all: diapers, story time, feedings and even sing-a-longs.

“When Charlotte has challenges teething, ‘The Wheels on the Bus’ song can go on for hours,” Chelsea told PEOPLE. “Like, everything gets on the bus – every animal from Old MacDonald’s farm gets on the bus, everybody we know gets on the bus So my mom is very sweet when she’s singing ‘The Wheels on the Bus.’ ”

Thanks to grandma Clinton, whenever little Charlotte hears the song “Twinkle, Twinkle, Little Star,” she imitates the twinkling of stars by scrunching her hands together.

“It’s very sweet,” Chelsea told PEOPLE. “She learned that from my mom.”

• Reporting by SANDRA SOBIERAJ WESTFALL