The results of individual special elections, like Thursday's in Montana between Democrat Rob Quist and Republican Greg Gianforte, can't always foretell what will happen in the next high-stakes midterm. Each district presents its own unique set of variables, like flawed candidates or dreadfully unpopular governors. But taken collectively, the margins in specials can tell us a good deal about the political environment — and so far, it's looking really bad for Republicans. There's no such thing as a "make or break" special election. In June 2006, Democrats fell four points short in a nationally hyped San Diego special election. In May 2010, Republicans fell eight points short in a Western Pennsylvania special. In both cases, the losing side wrested control of the House just a few months later. However, that doesn't mean we should disregard specials, either. In fact, there's a smarter way to draw meaningful conclusions from them than simply looking at who won and who lost. So for special election watchers, here's my step-by-step guide:

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