For this moment in national polling, "Cain is the leader ... That's the story," said Democratic pollster Peter D. Hart to NBC News. Or at least he's close. Hart conducted the latest NBC News/Wall Street Journal survey, which backs up that sentiment with these numbers: Cain topped the field among GOPers, nabbing 27 percent to perennial frontrunner Mitt Romney's 23 percent and free falling Rick Perry's 16 percent. That poll runs in a similar vein to yesterday's Public Policy Polling heat check, which has Cain leading the field, and the Reuters/Ipsos poll showing the former pizza CEO in a close second to Romney.

Cain is just the latest GOPer to try to snatch the frontrunner mantle from Romney. Just look at the intersecting squiggly lines of Real Clear Politics's aggregate polling chart for the last six months. Since they're showing running averages, it doesn't show Cain (he's the red line) in the lead quite yet, and one-time frontrunner Donald Trump isn't shown at all. Still, you can see how fluid the race has been. (Or, if you prefer an actual horse race, Slate's nifty race track feature using the same data.)

The NBC/WSJ poll underscores quickly that fragile political fortunes can turn. Last time survey was conducted, in August, "Perry led the field at 38 percent, Romney stood at 23 percent, while Cain was at only 5 percent."

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Erik Hayden