It wasn't the only jab Rubio made at Trump's appearance.
Trump's hands have long been a target of jokes from his critics. In November, Vanity Fair's Graydon Carter wrote how Trump for years remained indignant that Carter had described him 25 years ago as a "short-fingered vulgarian." In response, Trump over the years would send photos of his hands, Carter wrote.
"I almost feel sorry for the poor fellow because, to me, the fingers still look abnormally stubby," Carter wrote.
It's become a frequent troll of Trump among some conservatives and libertarians. In January, Sen. Ben Sasse joined in.
But what do they say about men with small hands? Per Rubio: "You can't trust 'em."
Claudia Koerner is a reporter for BuzzFeed News and is based in Los Angeles.
Contact Claudia Koerner at firstname.lastname@example.org.
Got a confidential tip? Submit it here.