Katrina Pierson, national campaign spokeswoman of GOP presidential nominee Donald Trump, said Monday that Weekly Standard editor Bill Kristol should realise that he can never beat Trump and that the “Never Trump” campaign is selfish.

“People like Bill Kristol still don’t get it,” Pierson said on CNN’s “New Day” program. “Mr. Trump has broken the record in GOP primary turnout. Bill Kristol is actually trying to form a party against the Republican Party itself.”

The Weekly Standard editor posted a tweet on Sunday indicating the possibility of an independent presidential candidate entering the race. CBS News reported that he said nothing more than describing the possible candidate as “an impressive one, with a strong team and a real chance.”

In response to the post, Trump unleashed a series of insults towards Kristol, calling him “dummy” and an “embarrassed loser.”

“If dummy Bill Kristol actually does get a spoiler to run as an Independent, say goodbye to the Supreme Court!” Trump tweeted. He even called on the Republican Party to be strong and not allow lightweights to spoil the chances of his coming to power in November.

“Bill Kristol has been wrong for two years — an embarrassed loser, but if the GOP can’t control their own, then they are not a party. Be tough, R’s!” he said in another tweet. In reply to Trump’s comments, Kristol tweeted on Monday that he is sorry that he didn’t realize that a mere mention of an independent candidate had so unnerved him.

Pierson said that Trump has been able to win the support of those people who wanted a third party to take part in the race because he was not from a political background. She reiterated that the intention behind the Never Trump movement is selfish.

“He does talk about a third-party candidate getting in the race and essentially handing over the presidency to Hillary Clinton,” Pierson said Monday as quoted by Newsmax. “That’s nothing new. Bill Kristol knows this. So the intention is selfish for someone like Bill Kristol and the ‘Never Trump’ movement to even try something like this.”