A lot of people tend to focus on spelling in their writing, and indeed, spelling mistakes and typos can be embarassing. But it seems to me the real work horse in proper written expression is punctuation. Consider the difference:
– “Oh yes.”
– “Oh, yes.”
Meanwhile, the phrase “John McCain harkens from antideluvian times” has two spelling errors, but the point that John McCain is ancient isn’t strengthened by spelling “hearkens” or “antediluvian” correctly. Just saying.