This morning, regular Fox News and CNBC guest and Mitt Romney surrogate Donald Trump tweeted that Huffington Post founder Arianna Huffington “is unattractive both inside and out. I fully understand why her former husband left her for a man- he made a good decision.”

Trump makes weekly guest appearances on Fox News' Fox & Friends and on CNBC's Squawk Box. He often uses those appearances to offer baseless conspiracy theories about President Obama. Indeed, CNBC.com has noted that Trump “has been at the forefront of the 'birther' movement -- those who question whether Obama was born in the U.S.”

Shortly after Trump's appearance on CNBC this morning, the program hosted Huffington, who criticized the Republican National Convention for devoting insufficient attention to job creation.

Last year Fox News relentlessly promoted his claims that President Obama was not born in the United States. Earlier this month on CNBC, Trump used an appearance to claim that Mitt Romney should only release his tax returns if Obama releases his college transcripts, echoing a right-wing conspiracy that those documents indicate that he attended college as a foreign student.

UPDATE: In a subsequent tweet, Trump says of Huffington, “if you knew her and the phony Huffington Post you would understand” the harshness of his attack, and promises “more to follow.”