Pagerank and duplicate content

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I know that if you have duplicate content on your website, you'll be punished with lower pagerank. Now I have 2 blogs that I use. I copied some posts from old blog to the new one and also posted some entries to both cause they share the same topic. Now I don't care about my old blog at all, I don't really use it anymore. The old one has 10x less visitors and 3x less backlinks but it has pagerank 2. The new one has 1. Now if I delete all the posts on the old blog, will that increase the rank of the new one or is it cursed forever?