Not a big fan of Rush but in defense of Rush, he NEVER called Chelsea Clinton a dog.
The fact is, Rush Limbaugh never calls Chelsea a "Dog" verbally but his reference to her as a dog by juxtaposing a picture of a dog in reference to her name is hardly much of a difference.
I apologize for the YouTube misdirection. I checked the YouTube set up again it directed to the Limbaugh comment. Unless, it's verboten here at FR.
The You Tube video worked the second time, so you can see for yourself that at the very least it was implied.