I'm sure it was just an oversight, just like all the rest...riiiight. Have I missed any?
It's almost a clockwork thing.
Whenever Fox News wants you to forget that someone is actually a Republican, they, ah, accidentally label them a Democrat on their chryon and let it go. So they did that today, as you can see, while Mark Sanford was explaining that he had been in Argentina to screw around on his wife. (They corrected it in later chryons.)
At other times with sex scandals, as with Sen. Larry Craig, they simply have forgotten to identify them as Republicans.
They've also done it when someone's Republican status is inconvenient:
When Arlen Specter was attacking conservative shibboleths, he got labeled a D too.
And then there was the time John McCain was labeled a Democrat too. At the time that just seemed weird, but now, with Glenn Beck and Rush Limbaugh and a host of other conservatives promoting the notion that McCain was just a fake Republican anyway, it makes a certain kind of sense.