As the participation of actual voters in the 2008 presidential contest grows nigh, polls are rolling out at an ever-increasing pace (here, here, and here, just yesterday).

Put 'em all in a bag, shake 'em up, roll 'em back out, and the Big Picture becomes pretty clear:

On the Democratic side, Iowa remains skin-tight among the Big Three of Clinton, Obama and Edwards, and now NH and SC are tightening up as well. Whoever wins Iowa will almost certainly become the instant front-runner in the other two contests. And with no really clear front-runner anymore, "exceeding expectations" in IA may not be much of a factor. It's all about win, place or show, and show is unlikely to cut it. Moreover, unless something really strange happens, the non-Big-Three candidates will all struggle to survive Iowa.

On the Republican side, there are now four candidates with a plausible route to the nomination: Huckabee, Giuliani, Romney and McCain. Huck's got a growing lead in IA and national momentum; Romney's got a sizable lead in NH and unlimited money; Rudy's got February 5 plus the possibility that Huckabee and Romney will fatally wound each other; and McCain's got enduring support in NH and, well, a growing sense that nobody else is broadly acceptable.

It's going to be a wild ride beginning on January 3.