To win Pennsylvania, Barack Obama must pull off a “Missouri” -- that is, do what he did in the Show Me State: win a handful of heavily populated, liberal-centric counties and call it a day.

Ironically, that is what Ed Rendell (a Hillary Clinton supporter) did to Bob Casey (an Obama supporter) in Pennsylvania’s 2002 Democrat gubernatorial primary.

Pull out an old red-blue county map of the 2002 race, and it is hard to believe that Casey won 57 counties to Rendell’s 10 and still lost the race. Yet lose he did, 56 percent to 44 percent. His loss was felt throughout the state party organization that endorsed him and the labor unions that invested millions in his campaign.

In Democrat primaries, Pennsylvania’s political geography is not what party strategist James Carville once cited -- Pittsburgh in the west, Philly in the east and Alabama in the middle. It is more like Philly and her collar counties to the east and nothing but a Midwestern state from there to the Ohio border.

There is much value for the Obama and Clinton camps to glean from the Rendell-Casey showdown, which was the most expensive primary race in state history; the voting trends reflected in that year’s electoral map have only solidified the last six years.

Ed Rendell won by a small number of counties, but those he won counted big. In the southeast, he racked up Bucks, Chester, Montgomery, Delaware, Berks, Northampton, Lancaster, Centre, Philadelphia and Lehigh counties. Most strikingly, he won some precincts by 80 percent.

Casey’s problems began when his team started running a personally negative campaign, attacking Rendell on education and city of Philly failures. That approach sealed the deal for Rendell with southeastern voters. The media there built up Rendell as having saved Philly as its mayor; they barely covered Casey, nor allowed him to gain traction.

That left Casey playing in four big yet less-populated areas: the Northeast corridor and Scranton (his base), the Southwest corridor, Altoona/Johnstown and Erie.

Rendell also expanded into South-Central Pennsylvania, cutting into what should have been Casey’s area. That was the difference in winning and losing the race.

Another problem for Casey was his message: In his stump speeches, he talked about his father’s passion to help the “steelworker in Monessen.” He never understood that there are no more steelworkers left in Monessen.

Rendell’s message was simple: change.

The Clinton-Obama race shapes up as similar to Casey-Rendell, but the Pennsylvania players are reversed.

Rendell is with Clinton, who is the Casey of this race; she plays to the same demographics -- conservative Catholic Democrats. To hold her lead and win, she must spend time in Southeastern Pennsylvania and try to appeal to its suburban Philadelphia's “soccer moms.” Continued...