They do this on purpose and they invest a lot of money into it if they need to, bringing Tina Fey back could not have been cheap.
They will pay for expensive talent to portray a republican they want to stop and the media takes the skit portrayals out into the voting public and helps them stick.
Yes that is exactly what they do. That is why the Trump memes give them fits. He is using one of their most potent weapons against them.