Here's a key thing to understand about Feb 5: 

In Democratic races, most congressional districts select between four and six delegates. The exact number will be determined by Democratic performance in the 2004 presidential election and recent state elections, with more delegates awarded to heavily Democratic areas.

In a race with two strong contenders such as Obama and Clinton, analysts said, the candidates are likely to split the delegates evenly unless one wins by a significant margin.

Devine said that because "you have to win a district by an enormous margin" to gain the extra delegate in a six- or four-delegate district, candidates may spend less time and money there unless they think there is a chance for a blowout win.

Congressional districts with an odd number of delegates are a different story. In those districts, winning by just one vote translates into an extra delegate. In Massachusetts, three congressional districts - the Fourth, Fifth, and Tenth - have an odd number of delegates.

In general, Devine said, the Democratic campaigns are eyeing "threshold" figures in each district to determine where to direct resources. If a candidate is polling at 56 percent in a six-delegate district, it might make sense to buy more advertising there in hopes of pushing support up a few points to claim the fourth delegate. For instance, the Clinton campaign planned rallies yesterday in heavily Latino sections of Los Angeles, where the candidate is expected to cruise to victories over Obama, in the hopes of running up the score there and raising the delegate count.

It's going to be very difficult for either Clinton or Obama to wake up Wednesday with a commanding lead. But there should be some battle royales in those odd-numbered districts, upon which I suspect national reporters are already descending. 

--Michael Crowley