Apostrophe Question

[gjo123]

The following sentence appeared in my morning newspaper today. Is the apostrophe on the word socialist correct? If so, what makes it correct?

"But if Rush Limbaugh calls Obama a socialist, maybe a socialist's not such a terrible thing to be."

Of course, I can see that the apostrophe could render the meaning to be "socialist is," but it "looks" like a word meant to be in the possessive case. In this sentence, the term cannot be in the possessive case as I see it. So can an apostrophe be added onto the end of any word, just before the letter "S" to make the term = X is?

[gabber]

Yes, the " 's " can be added to the subject of the clause that it is in to mean "is," or "has." The context shows which auxiliary is appropriate. [The "is" or "has" is the finite verb for the clause it's in.]

[Mike the cool person]

The apostrophe is there as an abreviative replacing 'is'. Maybe a socialist is not such a .....