Senor Danger may have just lost the senior-citizen vote.

Anthony Weiner went after his elder GOP opponent George McDonald yesterday, sarcastically referring to him as “grandpa” at, of all places, a forum sponsored by the AARP.

The standoff started just before the debate, when the 48-year-old Weiner put his hands on the 69-year-old McDonald’s chest as he walked by, possibly to say hello.

McDonald quickly flew into Weiner’s grill.

“Don’t put your hands on me ever again,” McDonald growled, as the two stood nose-to-nose.

“What’s gonna happen if I do?” Weiner asked, then continued: “You have anger issues.”

ONE FOR THE AGES: GOPer George McDonald goes at it with Anthony Weiner yesterday at an AARP in Queens, where Weiner unleased his “grandpa” insult.

“I don’t have anger issues,” McDonald insisted.

“Yes, you do, grandpa,” Weiner appears to say, according to muffled video of the exchange captured on NY1.

McDonald remembered it differently.

“He said, ‘What you going to do about it, grandpa?’ ”McDonald told The Post afterward. McDonald said he became outraged after feeling “two hard slaps on my chest.”

“He reached around and slapped me with an open hand. It wasn’t some love tap,” McDonald said.

The feud between the two has been simmering since at least last week, when McDonald called Weiner a “self-pleasuring freak” at a forum at a church in Laurelton, Queens.

On WWRL this morning, Weiner said he called George McDonald “grandpa” because McDonald is always talking about his granddaughter at forums.

“He talks about his granddaughter in every answer on the campaign trail,” Weiner said, without mentioning why McDondald talks about his granddaughter.

At the Laurelton forum last week, McDonald said that he was embarrassed to tell his 10-year-old granddaughter just why Weiner is so famous.

“This past weekend I had a very uncomfortable conversation with my 10-year-old granddaughter Emma because she wanted to know why is this Anthony Weiner famous? ‘Why is he a celebrity, grandpa?’ And I honestly couldn’t explain,” McDonald said.

Weiner responded by calling McDonald a candidate “chirping at the fringes,” which only fanned the flame of McDonald’s temper yesterday.

During yesterday’s forum, McDonald kept on beating the Weiner-bashing drum.

“I want to say one thing about American values. I would contrast my values with Anthony Weiner’s values any day of the week,” McDonald said.

Political experts say Weiner’s “grandpa” quip is sure to hurt him with seniors — who made up of a third of the electorate in the last open mayoral election — and whom Weiner has been working hard to court in the past several weeks.

“It can’t have a positive effect. Data consistently shows that older people vote in the greatest numbers,” said Baruch College political science professor Doug Muzzio. “Is this how he’ll govern — by insult? It’s increasingly mind-blowing that he can be so self-destructive.”

Weiner has campaigned at several senior centers, including in Flushing last week and in Elmhurst Monday, where he passed out cookies to seniors and promised that if elected, he will make it easier for them to cross the street.

Weiner spokeswoman Barbara Morgan, who became famous herself last week for a foul-mouthed rant against a former intern, said she had no comment on Weiner’s “grandpa” remark.

The AARP was not amused.

“It’s unfortunate that the term was used,” said AARP spokesman David Irwin. “We don’t think age should be a considered when running for public office, or for anything else for that matter.”

However, Weiner did stick up for another older candidate yesterday — Green Party candidate Tony Gronowicz, who was pulled out of the debate by police after AARP officials refused to let him participate.

When the candidates were called onstage, Gronowicz went up but was then told he wasn’t invited.

“It was kind of strange, considering that I’m 68 years old, that AARP would throw me out,” he said.

According to Gronowicz, he picked up the microphone and said he was the Green Party candidate. CUNY security then turned the mike off. He tried another three mikes then six security guards grabbed him, “and I fell down,” Gronowicz said, adding that he wasn’t seriously hurt.

Weiner shouted: “Let him stay!” to no avail.

bdefalco@nypost.com