But, if you read the article, that's exactly his point. He is trying to identify all the straws that Democrats want to grasp -- and then effectively destroys them.
His conclusion is that the Republicans are most likely take control of the House by a significant margin. But, he points out that a huge blowout (70+ seats switch to Republican) is unlikely, and that the Democrats holding on to control of the House is just as unlikely.
You are right, of course. I grow respect for him. He provides a window of what might go well for the Dhims, but he also has written before what might go for very well for the Republicans.