It was an honest mistake by a first-time voter.

Sandro Marcos, son of vice presidential candidate Ferdinand "Bongbong" Marcos Jr., admitted Tuesday that he mistakenly shaded Grace Poe for president while he was preparing to vote for his father on the May 9 polls.

"Yes, I shaded two presidents, it was an honest error on my part," said Marcos.

Marcos, a first-time voter, said he first picked Rodrigo Duterte for president but shaded on another candidate's slot, invalidating his vote for president.

"I was a first time voter and extremely nervous. I voted for Duterte as president, and saw the number 4 right after, so shaded that as it was my dad's number. I ended up shading Poe's name instead of my dad's, so my presidential vote didn't count," said Marcos.

He asked people to lighten up, saying errors are normal.

"Once again, it was an error on my part, and I think people need to relax a little bit. We all make errors now and then," added Marcos in a post in his Facebook page.

But thankfully, Marcos got his vice president right.

"At least my VP vote was right ;)," he said.

Sandro said he did not vote for his father's running mate, Miriam Defensor-Santiago.

"She was my first choice, but I decided last minute to switch. Everyone is entitled to their own political opinion," Marcos said.

The young Marcos also said the "fight still continues" for his father who is in a tight race with Liberal Party bet Leni Robredo. The Marcoses have cried fraud, claiming cheating from other parties after a supposed "glitch" in the transmission of votes.

"The fight still continues, and the events that came after the 'glitch' of the vote counting when my dad started going down, are questionable at best. Nevertheless, we carry on as best as we can and seek the truth on that part," he said.

Bongbong earlier called on the Commission on Elections to terminate the unofficial count immediately amid claims of ''dagdag-bawas'' or vote padding-shaving.