Donald Trump took to Twitter Sunday night to slam fresh predictions from Weekly Standard editor Bill Kristol that an independent candidate would soon be entering the race for president, warning that a 2016 “spoiler” could swing the race to the Democrats.

Kristol, along with other conservative pundits, long has been working to attract an independent candidate to run in November amid lingering concerns in some wings of the Republican Party about Trump’s conservative credentials. This effort to date has struggled to recruit a willing candidate, while running into logistical hurdles -- including the rules and deadlines for getting new names on the ballot.

Yet on Sunday, Kristol teased a forthcoming announcement, saying on Twitter:

This prompted the flurry of tweets from presumptive Republican nominee Donald Trump, whose claim to the nomination was affirmed last week with a fresh Associated Press tally that showed him with more than the 1,237 delegates needed to clinch it. Trump, while taking some personal shots at Kristol for good measure, warned that an independent bid could hurt the GOP in the fall.

Former 2016 candidate and Trump backer Ben Carson, speaking Monday on Fox News, echoed Trump’s warnings and invoked the 1992 presidential race as an example.

“A quarter of a century ago, another Clinton was running for the White House, and it was the entrance of a third-party candidate, Ross Perot, that made it possible for him to win,” Carson said. “Wouldn’t it be ironic if the same thing happened this time?”

Asked who, if anyone, might run, Carson said he’s heard “rumors like everyone else has” but did not offer a name. But he urged any prospective candidate to “stop for a moment and think about what the implications are of allowing Hillary Clinton” or a candidate like her to win.

Carson, like Trump, is effectively warning that any independent candidate would at this stage draw votes from the Republican nominee, potentially tilting the election to likely Democratic nominee Clinton.

Perhaps the one talked-up independent prospect who might draw votes away from Clinton, former New York Mayor Michael Bloomberg, already has made clear he has no plans to run.

Yet prominent Republicans like Mitt Romney, the party’s 2012 nominee and an outspoken Trump critic, so far have balked at mounting an independent bid.

Romney reportedly was among the potential candidates Kristol has tried to recruit.

Meanwhile, at least one third-party ticket could be a factor in November, whether or not an anti-Trump independent bid materializes. The Libertarian Party over the weekend selected former New Mexico Gov. Gary Johnson as their nominee – a candidate who has polled at about 10 percent in recent hypothetical match-ups against Trump and Clinton.

“I think the Libertarian Party actually represents most people in this country, but they just don’t know that they’re Libertarian,” Johnson told Fox News on Monday.