What's Mallard raving about today?
Mitt Romney, GOP Candidates
What they mean by "presidential" is that by contrast to the other GOP candidates, he's not bat-shit insane.
What they mean by "flip-flopper" is that he is now doing his best to appear as bat-shit insane as the rest of the GOP candidates, because that's what Republican voters like you want.
What any of this has to do with President Obama is something known only to Mallard, of course.
One can guess that he thinks it's automatically hilarious to insinuate a pejorative about President Obama, regardless of whether there's anything truthful (or funny) about it. For this reason, no one ever describes Mallard Fillmore as "funny".