Donald Trump did not wait to reply. Less than two hours after Weekly Standard editor Bill Kristol sent out a tweet that said there would soon be news of an “impressive” independent presidential candidate, the presumptive Republican nominee went on the attack. In a series of tweets, the real estate mogul called Kristol a “dummy” and an “embarrassed loser.” He then said Republicans can “say good bye to the Supreme Court” if an independent contender does materialize.

It all started with a mysterious-sounding tweet from Kristol in which he assured readers that “there will be an indepenent candidate” who is “impressive,” and has “a real chance.”

Just a heads up over this holiday weekend: There will be an independent candidate--an impressive one, with a strong team and a real chance. — Bill Kristol (@BillKristol) May 29, 2016

Trump quickly fired back, first calling on Republicans to “be tough.”

Bill Kristol has been wrong for 2yrs-an embarrassed loser, but if the GOP can't control their own, then they are not a party. Be tough, R's! — Donald J. Trump (@realDonaldTrump) May 29, 2016

He then characterized Kristol as a “lightweight” who was trying to “set up a spoiler Indie candidate”

The Republican Party has to be smart & strong if it wants to win in November. Can't allow lightweights to set up a spoiler Indie candidate! — Donald J. Trump (@realDonaldTrump) May 29, 2016

And proceeded to warn of the consequence that a “spoiler” candidate would have on the Supreme Court.

If dummy Bill Kristol actually does get a spoiler to run as an Independent, say good bye to the Supreme Court! — Donald J. Trump (@realDonaldTrump) May 29, 2016

Kristol’s brief, mysterious message was interesting considering the timing. It came mere days after Kristol said in a Bloomberg podcast that Mitt Romney was seriously considering a third-party candidacy. “The real last chance here is with Mitt Romney, who has said ‘no’ but who I think is thinking seriously about it,” Kristol said last week. “He is a very serious person, he really knows that Trump should not be president of the United States. He strongly believes that Hillary Clinton should not be president of the United States.” Earlier this month, Yahoo News reported that Romney had ruled out an independent presidential candidacy.