Why do the media put a "R" next to the name of a politician in a scandal, but never put a "D" by the name?

I have noticed this year after year now. If it is a Republican there is always a (R) after the name. If the politician is a Democrat they rarely if ever put a (D) after the name. You have to read the story and half the time they don't tell you their affiliation in the story either. You have to Google the politician's name.