CQ Politics has been doing a great job parsing the proportional allocation rules in Democratic primaries, and their Indiana write-up is a must read.

The takeaway: In all but one of Indiana’s congressional districts (the unit by which most delegates are assigned), there are an even number of delegates available:

There are four Democratic delegates assigned to the Republican-leaning 3rd, 4th and 5th districts and six delegates in each of five districts that are more friendly to Democrats—the 1st, 2nd, 7th, 8th and 9th. The 6th District has five delegates.

It’s notable that eight of the nine districts have an even number of delegates. Because of this, a wide range of vote percentages for the candidates will yield delegate ties of 2-2 or 3-3. In the four-delegate districts, Clinton or Obama would need 62.5 percent of the vote to garner a 3-1 delegate split; anything lower than that would yield a 2-2 tie. In a six-delegate district, the winner would need 58.3 percent of the vote to turn a 3-3 tie into a 4-2 edge.

That accounts for 47 delegates; the other twenty-five are allocated by statewide vote, but again, there are smaller units of division that increase the likelihood of ties.

The other 25 pledged delegates at stake—16 “at-large” delegates and nine party leader and elected officials (PLEOs)—will be distributed in proportion to the statewide vote. The 16 at-large delegates will split 8-8 if the winner takes less than 53.1 percent of the vote. The statewide winner is guaranteed a 5-4 victory among the nine PLEOs; it would require 61.1 percent of the statewide vote for a 6-3 edge.

It’s entirely possible, CQ writes, that a 6-point win for Clinton would net her just one delegate.

But I love this part. The easiest way to pull a delegate one way or another in Indiana is to zero in on the single 5-delegate district. Sounds like Obama should be pulling out all the stops in Ball State University in Muncie.

• 6th District (East — Muncie, Anderson, Richmond). Indiana’s 6th, represented in Congress by Republican Mike Pence , is the only district with an odd number of district delegates (five), so either Clinton or Obama will emerge from here with a 3-2 edge. (It takes a 70 percent supermajority for a 4-1 split). The university community in and around Ball State University in Muncie is likely to lean Obama, but Clinton should otherwise do well elsewhere in this district, which is overwhelmingly white and has levels of income and education that are lower than the state at-large—a profile that matches many other districts in previous primary states where she has done well. Fayette County, which includes Connersville in the southeastern area of the district, has the highest unemployment rate of any of Indiana’s 92 counties. CQ Politics Projection: Clinton 3, Obama 2.

Unfortunately for Obama, this is finals week at Ball State—good luck getting the kids to stick around till Tuesday.