Red-meat rhetoric

Could anyone tell me about the word origin of 'red-meat rhetoric'?

"Red-meat rhetoric" can refer to a political speech which is loud, brash and in your face.

The image is one of a piece of beef dripping with blood ,very raw, uncooked or undercooked.

Most political speeches are well rehearsed and calm with an image of medium well done beef.

Many thanks, Bruce. I knew the meaning but am still wondering where this expression originally comes from. Does it carry a negative connotation of Red America? I mean red meat is a symbol of uncouthness,unsophistication and possibly uneducation? I guess conservative people in Red America stick to red meat, even though there are many more healthy alternative food such as fish, vegetable etc.

I think it is all in the imagery.
Someone giving a shoot-from-the-hip type speech, a la Al Sharpton at the Dems Convention, is giving a RAW speech, as it is dripping with emotion, fire and brimstone.