One way to measure the presidential race is to compare the national Gallup poll now to national Gallup polls taken on or close to this date in previous years to see their predictive value. Talking Points Memo has collected the data, and here it is. The notation D+6 means the Democrat was ahead by 6 points, etc. Incumbents are marked with an asterisk.
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(If there's one thing we know about comment trolls, it's that they're lazy)