Markets sour on both Romney and Obama speeches, but conventions boost Obama (Originally posted on Yahoo!'s "The Signal" Blog)

While the purpose of the political conventions was to draw clear distinctions between President Barack Obama and challenger Mitt Romney, the two men remain identical in one key respect: When they open their mouths before a national audience, their odds of winning in November suffer.

As you see here, the likelihood of Obama's re-election jumped about 1 percentage point immediately after Romney's address last Thursday evening, and fell slightly after Obama's turn last night. (The model for predicting the outcome of presidential elections relies on many contemporary and historical factors, but the fine-tuned reactions you see here are driven by prediction markets.)

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