You shouldn't have as much trouble with these because you don't hear them misused quite as often in this way. Any time a pronoun comes after one of these verbs, the subject form is required. It was they . The best thing to do when you write yourself into a construction like this is to rethink and rewrite in a different way. The dog down the street is meaner than she .
Dogs are as smart as they .
You could, but that wouldn't be right. There's an understood verb in the construction. Even though you probably hear these kinds of sentences used incorrectly, when you're writing you can get them right if you remember that understood verb. They can also be used to ask questions. Peggy is the dog whom everyone loves to pet.