The presidential campaign, through the prism of polls

The last round of presidential polls warned Americans that the race was so tight, it might not be settled Tuesday night. But pollsters were predicting a close race between President Obama and former Massachusetts Gov. Mitt Romney even before it was clear that Romney would be the GOP nominee. The incessant polling yielded volatile results, but the core message was that neither candidate was building sustainable momentum.

We'll know soon enough how accurate the pollsters were. In the meantime, here's a look back at what they've been saying over the last three years. --Jon Healey