BLUFFTON, South Carolina (AP) — Presidential candidate Donald Trump has pulled a classic adolescent prank by releasing the phone number of a rival who dared to criticize him, the latest chapter in an on-going feud between the billionaire real estate mogul and other candidates for the Republican presidential nomination.

After Sen. Lindsey Graham called Trump “the world’s biggest jackass” during a television interview, the billionaire developer read Graham’s personal cellphone number and showed it to TV cameras at a campaign event. Graham joked that he would have to buy a new phone. His voice mail quickly filled up.

Trump is now at odds with much of the Republican establishment after a series of incendiary comments, topped by his weekend mocking of Arizona Sen. John McCain’s experience as a tortured prisoner of war in Vietnam.

Since then Trump has intensified his criticism of McCain and his record on veterans issues in the Senate, even as politicians from both parties and veterans groups have rushed to the defense of McCain, the 2008 Republican presidential candidate.

Trump had shot to the top of recent polls of the crowded Republican field, but these were taken before the flare up over his comments about McCain.

Trump is still seen as a longshot for the Republican nomination, but his incendiary remarks have shaken up the early stages of the race, drawing attention away from other top-tier candidates like former Florida Gov. Jeb Bush, Wisconsin Gov. Scott Walker and Florida Sen. Mario Rubio. The latest Trump flare-up overshadowed Tuesday’s campaign launch by Ohio Gov. John Kasich.

In a speech Tuesday to hundreds of supporters in Bluffton, South Carolina, Trump kept going after McCain, accusing him of being soft on illegal immigration.

The reality television star also went after others who have criticized him in recent weeks, implying that former Texas Gov. Rick Perry was unintelligent and Bush was weak.

McCain sparked Trump’s temper last week when the Arizona senator said the businessman’s inflammatory remarks about Mexican immigrants had brought out the “crazies.” McCain said Tuesday he would no longer respond to Trump’s comments.

Graham, a McCain friend and one of the 16 notable Republicans running for the presidential nomination, betrayed the growing exasperation and anger of many in the party when he appeared earlier on “CBS This Morning.”

“Don’t be a jackass,” Graham said. “Run for president. But don’t be the world’s biggest jackass.”

He said Trump had “crossed the line with the American people” and predicted this would be “the beginning of the end with Donald Trump.”

Trump responded during his speech by calling Graham an “idiot” and a “total lightweight,” then held up a piece of paper and read out the senator’s cellphone number. He said Graham had given him the number several years ago when he’d asked him to put in a good word with a morning news show.

“Give it a shot,” Trump encouraged. “He won’t fix anything, but at least he’ll talk to you.”

Graham’s voice mailbox was full Tuesday afternoon. Spokeswoman Brittany Brammell confirmed the number was his. Graham tweeted later: “Probably getting a new phone. iPhone or Android?”

Elsewhere in South Carolina on Tuesday, Bush walked a fine line, criticizing his fellow candidate’s rhetoric on immigration and McCain as “divisive” and “ugly,” but saying Trump’s supporters are “good people” with “legitimate concerns.”

Associated Press writers Meg Kinnard in Bluffton, South Carolina, Jill Colvin in Newark, New Jersey, Bill Barrow in Spartanburg, South Carolina, and Jonathan Lemire in New York contributed to this report.