"Now, some of Trump’s longtime advisers are even urging him to continuously make reference to the size of DeSantis’ penis..."

"... telling him such insults could stick with GOP primary voters and mess with his rival’s head, two sources with knowledge of the matter tell Rolling Stone. Trump’s team discussed having Trump refer to the Florida governor as 'Tiny D,' Bloomberg reported in March. While some understood it as a shot at DeSantis’ height, the sobriquet was specifically intended to suggest diminutive genitalia, four people familiar with the topic say. 'He’s also short but … yes of course it’s about his penis, that’s why we’re doing it,' says a source involved in the effort to get the former president to use the line of attack against DeSantis."

From "Oh-So-Mature Trump Aides Want Him to Focus on DeSantis’ Penis/The 2024 GOP primary is headed for the dumbest places imaginable" (Rolling Stone).

Over in New York Magazine, there's an article called "Donald Trump’s Nasty Ron DeSantis Nicknames, Ranked," and "Tiny D" is listed as #3 (after "Meatball Ron" and "Rob"):

Feedback: “Tiny D” represents DeSantisis’s “pro–toxic masculinity culture wars” coming back to bite him, as Jezebel put it. At around five-eight to five-ten, the governor is kind of short for a presidential candidate, and he’s been wearing high heels to cover this up. So “Tiny D” could be read as an attack on DeSantis’s height, his insecurities, and his effeminate footwear choices.

Also, it sounds like Trump is saying his dick is small....

“Tiny D” isn’t a slam dunk, in my view, but it’s workable. And it is a nice callback to Trump’s roots (i.e., assuring 2016 GOP primary voters that “there’s no problem” with his penis size).