Donald Trump seems a little perturbed at the possibility of an independent candidate entering the presidential race, even though he once threatened to run as an independent.

Conservative political pundit Bill Kristol tweeted a cryptic message over the weekend suggesting an independent candidate is coming to challenge Trump and Hillary Clinton.

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Trump's response included calling Kristol a "dummy" and warning that an independent candidate would hand the election to Clinton.

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Aside from the fact the GOP contender is still referring to his own party as "they," it's strange that Trump is so sour on the idea of an independent candidate.

Just three months ago, Trump was renewing a threat to run as an independent himself because he thought the Republican Party was being unfair to him.

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"I am watching television, and I am seeing ad after ad after ad put in by the establishment, knocking the hell out of me, and it's really unfair. But if I leave, if I go, regardless of independent, which I may do — I mean, may or may not," Donald Trump said on MSNBC in March.

Another conservative candidate could siphon votes away from Trump and severely undermine his chances in the general election.

This video includes clips from Donald J. Trump for President Inc. and images from Getty Images.