Barack Obama is going below the belt when it comes to Donald Trump … joking that his successor is wearing diapers beneath his suits.

The former president is hitting the campaign trail and stumping for Kamala Harris in Pennsylvania, which figures to once again be a crucial swing state in the 2024 election, and he poked fun at Trump at a rally Thursday night in Pittsburgh.

Obama was talking about Harris wanting to make it easier for parents to afford everything they need to raise kids, including diapers … and he recalled for the first time he went to a store to buy diapers back in the day, and asked the crowd if they thought Trump ever changed a diaper.

Someone in the crowd blurted out that the only diaper Trump ever changed was “his own” … a comment that got a big smile and a hearty laugh out of Obama.

Barack responded, “I almost said that, but I decided I should not say it” … and he laughed again, as did lots of folks at the rally.