Clinton will probably drop out of the race in the next few days, so let’s give the diagram showing both of them one last airing. This looks at a month’s worth of polling data to give a picture of how their relative chance of victory has changed over time – it’s an animated GIF, so you’ll need to have GIF animation enabled in your browser.
She’s moved from being a percentage point below Obama to two percentage points ahead of him. What changed so much over the course of May? My guess is simply that people who aren’t natural Democratic voters are more likely to feel warmth to Clinton the further the nomination gets from her grasp, and we’d be seeing the exact opposite picture if it were Clinton who was expecting the concession call any day now.
Update: more commentary on this curious shift that seems to make a similar point.