Well, that didn't take long. A day after former South Carolina governor Mark Sanford announced that he'll challenge Donald Trump in the Republican Party's primary contest, the president made things personal by ridiculing him on Twitter over his infamous extramarital affair in 2009. “When the former Governor of the Great State of South Carolina was reported missing, only to then say he was away hiking on the Appalachian Trail, then was found in Argentina with his Flaming Dancer friend, it sounded like his political career was over. It was,” wrote the president. He added: “But now take heart, he is back, and running for President of the United States. The Three Stooges, all badly failed candidates, will give it a go!” Sanford joins former Massachusetts Governor Bill Weld and former lawmaker Joe Walsh as the three Republicans challenging Trump for the 2020 nomination.