sourcing isn't about the presence or not of a [3] next to your wild claims
it's about having engaged with work other people have done on the subject. Like, actually read and understood other people's ideas. You can really tell the difference between someone who just googled things to support whatever they wanted to say vs someone who is straight out the gate with "there are three prevailing schools of thought on this issue; the first, characterized by xyz, posits that abc" and so on
You think that Nate Silver used Google to find out about the American political landscape? Don't you think that the many years he spent working in a field where he learned a lot about American politics would have made him pretty well-informed on the topic?
The question is, which perspectives did he expose himself to during that time, and what did he conclude from those inquiries? Data is easy; interpretation is hard. It's not enough to say he had an accurate model, it has to be reasonable, too.
