If you can’t win, you might as well go down swinging.

At senior citizens.

At an AARP-Univision mayoral forum this morning, mayoral contender Anthony Weiner pulled out the age card to taunt his most vocal challengers, 69-year-old Doe Fund founder George McDonald. Weiner is 48.

Before the debate, Weiner put a hand on McDonald’s back and said hello, prompting McDonald to reply: “I would appreciate if you would never touch me again.”

Weiner retorted: “What are you going to do about it, grandpa?” according to two sources.

A mild overreaction by McDonald, but in his defense, who knows where that hand has been? Speaking of which, watch below as the future First Gentleman of the United States does his “Anthony who?” shtick when asked about the mayoral race. Nice job by the reporter too in reminding the world that the Clintons are sufficiently close to Weiner and his wife (“a surrogate daughter”) that Bill ended up officiating at their wedding. Makes the “we have lots of buddies in the mayor’s race” spin that follows ring even hollower than it otherwise would have.

How bad must a sex scandal smell to make even the Big Dog run from the stench? This bad:

Serial sexter and mayor wannabe Anthony Weiner appeared to be embracing his embarrassing online pseudonym and encouraged crowds that chanted, “Carlos!” and “Carlos Danger!” while marching in the Ecuadorian pride parade yesterday.

Sporting bright blue pants, a bullhorn and an Ecuadorian flag, Weiner repeatedly shouted, “Que viva Ecuador!” to the crowd as he energetically ran down Northern Boulevard in Queens with his loyal interns following.

That’s the difference between Weiner and the Clenis. You can picture Clinton sexting with admirers; you can’t picture him embracing his ridiculous alias in hopes that some of the voters who are laughing at him might vote for him for funsies, or out of pity. There’s an unusual desperation to Weiner’s foibles that most sex scandals, Clinton’s or otherwise, never quite sink to, and I think that encourages critics to beat up on him — even though, ironically, his sins are less severe than most adulterous pols’. Case in point: It’s hard to imagine Clinton getting called out like this by a voter, even in his pre-presidential days.

Weiner: “OK, OK — you’re very passionate.”

Borock: “I’m passionate? More passionate than you on Twitter! I’m a social media expert! You should get someone to handle your s—. You are disgusting.”

Weiner: “OK, you’ve had your say.”

Borock (to quickly gathering reporters): “F— you all for …”

Weiner: “Whoa, whoa. There are little kids here.”

Borock: “Little kids? You have no right to talk about little kids! Social media? Want to see some Twitter action?”

I wonder if Spitzer, who broke the law he swore to uphold to get sexual satisfaction, has ever had someone get in his face like that. What is it about Weiner? Is it just that he’s especially bad at feigning shame? Is it that he has no record to run on, so voters feel less compunction in treating him like the sleazy careerist pol that he is? Is it just the name? Clinton’s sex scandals would have had more traction if he’d been “Bill Scrotum,” I suppose. (President Scrotum?) Exit question: What makes Weiner such an irresistible target?