Memo to those feuding with Donald Trump: Hide your phone numbers.

Trump, the real-estate mogul and reality-TV star who has shot to the top of some polls for the GOP presidential nomination, on Tuesday gave out the cellphone number of rival Republican candidate Lindsey Graham.

The reason? A feud between the two White House hopefuls that’s been kicked into a higher gear.

Speaking at a rally Tuesday in Graham’s home state of South Carolina, Trump began criticizing Graham, calling him a “lightweight” and an “idiot.” Trump hurled the insults after Graham on Monday called Trump a “jackass” and said Trump’s recent comments about Sen. John McCain not being a war hero were the beginning of the end of the billionaire’s candidacy.

Trump later read out the phone number and said “Give it a shot.”

A Politico reporter called the number Trump read, and reached Graham. Graham said: “When it comes to the Donald, nothing surprises me anymore.”

Trump said he got Graham’s number a few years ago after the South Carolina lawmaker called him “begging” for a good reference with friends of Trump’s on Fox News’ “Fox & Friends” morning program.

Tuesday afternoon, Graham tweeted that he’s “probably getting a new phone.” And he asked for advice:

It might not be the last time Trump gives out a rival’s number, as another reporter speculated.

And it’s not the first time Trump has disclosed the phone number of a person with whom he’s feuding. Last month, he put a photo on Instagram of a letter to him from Univision anchor Jorge Ramos. The letter included Ramos’ personal cellphone number.

Univision cut ties with the Miss Universe organization, which Trump partially owns, in the wake of derogatory comments by Trump about Mexican immigrants.

Also read:The 2016 race features the most number of unqualified candidates