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Very few people watch political polls more closely than I do. (Whether that's a good thing or suggests that I'm slightly neurotic is up for debate.) When you monitor surveys incessantly, you occasionally see results that you're unsure how to interpret. You don't know whether they signal a key turning point in public opinion or whether they're just a hiccup, a passing blip. Or perhaps the odd results are from an outlier poll, a statistical anomaly that is the political equivalent of a false positive medical test.

We're currently experiencing one of those periods of uncertainty. One interpretation of recent results is that the momentum in this critical midterm election has shifted and the Republican wave has subsided. Another interpretation is that it's too soon to tell whether...