I'm going to be fair: To 'monkey' something up means to do something is a haphazard and careless way. I don't think I detect a specific racist intent here... or at least, that's more than enough plausible deniability. That's not to say he's racist, but I don't think he was trying deliberately to sound racist, at least. If anything, I'd imagine he's much prefer the GOP's normal brand of more insidious dog-whistling.