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.
The feud between the two has been simmering since last week.
At a debate in Laurelton, Queens on Thursday, McDonald called Weiner a "self-pleasuring freak." He said he was embarrassed to tell his 10-year-old granddaughter why Weiner was famous. Weiner replied then by calling McDonald a candidate “chirping at the fringes,” which only fanned the flame of the GOP candidate's temper.
As his support in New York dwindles, Weiner has been courting the senior citizen community by campaigning at numerous senior centers.