A freshman Nebraska senator dropped the ultimate trump card Friday night after Republican presidential candidate Donald Trump dubbed him a “gym rat” by playing libertarians’ new favorite internet game: joking about The Donald’s very small hands.

GOP Sen. Ben Sasse joined rivals Sen. Ted Cruz (R-TX) and Sen. Marco Rubio (R-FL) on the trail in Iowa in recent days with a simple message: stop Trump from being the party’s nominee.

Sasse’s new cause clearly rankled the Republican presidential frontrunner, who took to Twitter to call the senator “easy” and “totally ineffective,” among other attacks.

.@BenSasse looks more like a gym rat than a U.S. Senator. How the hell did he ever get elected? @greta — Donald J. Trump (@realDonaldTrump) January 30, 2016

But Sasse was undeterred, and tapped into a new meme among conservatives circles online for his counterattack: making fun of the billionaire for having small hands. Such criticism apparently really gets under Trump’s skin, with “Vanity Fair” editor Graydon Carter recalling in October that he still receives mail from Trump for once referring to him as a “short-fingered vulgarian” in “Spy” magazine:

To this day, I receive the occasional envelope from Trump. There is always a photo of him—generally a tear sheet from a magazine. On all of them he has circled his hand in gold Sharpie in a valiant effort to highlight the length of his fingers. I almost feel sorry for the poor fellow because, to me, the fingers still look abnormally stubby.

So, of course, conservatives have had a field day with The Donald’s meathooks:

Trump, Trump, he’s our man,

With a mouth as dirty as a garbage can.

Trump, Trump, crushing schlubs,

Tho his fingers are creepy stubs — Scott Lincicome (@scottlincicome) January 29, 2016

.@realDonaldTrump shakes hands to seal yet another successful business deal @TheRickWilson pic.twitter.com/zV41Z91w0D — Josh McCall (@JoshMcCall_) January 28, 2016

So then Sasse added this one to the mix:

Good grief. With a response like this you’d think I asked Mr @realDonaldTrump abt the length of his fingers or something important like that — Ben Sasse (@BenSasse) January 30, 2016

h/t BuzzFeed News