Now, I don't believe that "Broken Window Policing" stops major crime. I've seen reports claiming that crime dropped everywhere at the same rate as it did in cities where broken windows was touted.
The problem is that broken windows isn't something that would show short term gains. It's a long term - and only partial - solution. When I say long term I mean couple of generations not 10 years; unfortunately, I think this is too long for the program to keep any kind of political support. Pushback and the constant need to have a new politically exploitable program which each politician can claim as his own at the very least changes programs (i.e. Project Exile became Project Safe Neighborhoods).
These sorts of "simple" programs are not immediate impact programs. Instead, they are long term subtle impact programs. Their impact would be impossible to measure in a 10 year window. Crime rates in that period could be reflections of all sorts of societal matters ranging from the improbable - abortion brought down the crime rate - to the possible - a different demographic group among the lower classes has brought a different set of mores precluding a high crime rate. I'm not sure how you would measure it but if you were to measure the effect it would have to be over at least 2-3 generations of constant enforcement. If someone grows up and sees that no one care about his neighborhood or about the people in it that must have an impact. Broken windows, addicts panhandling or passed out in a doorway, people dealing on the corner, hookers walking the street, etc., none of these are things which produce a fruitful environment.
What happens when the police clamp down on these things? At first you get some superficial changes. Citations get the windows fixed. A young kid who "tags" the local market cleans the entire building as part of community service; an older kid who put him up to it gets detention or house arrest. The addicts and hookers and dealers move to alleyways or somewhere inside (BTW, this only works if "broken windows" is wide spread so that the whole show doesn't just move two blocks down). The people in the neighborhood are probably not all that happy because (1) no matter how many times people say they want law & order they are not all that happy when they are made to obey the rules (who wants his kid sent to detention for breaking a window? After all, boys will be boys), and (2) because they won't believe it; they've seen to many sweeps and crack downs where the police were there for a week or a month or maybe even a year or two, but the police always leave because something always ends up getting a higher priority - the trouble always comes back when they leave. People outside the neighborhood will be upset because (1) How dare they do this thing? They're arresting people for all sorts of garbage charges because they are [fill in your social group of choice]. Nobody in the affluent area of town gets arrested because he litters. and (2) because a lot of people outside the neighborhood own those crummy buildings which the locals rent for extremely low amounts. If they have to start fixing the buildings then they can't profit.
But what if the police continued to do broken windows policing and it became a matter of course? Everyone knows that a broken window is a citation offense if the owner doesn't fix it and the kid who did it will get punished if caught. Buildings and streets stay in better shape. The fact that the pushers, dopers, and hookers have been pushed off of and kept off of the streets may not actually stop crime, but it does emphasize that it is wrong and that police are looking for it.
Now imagine a third generation male growing up in a neighborhood under constant broken windows policing. His is still not a perfect life. He probably knows where the drug houses are and where he can go to find a prostitute. However, he doesn't have to run a gauntlet as he goes in and out of his apartment and walks to and from school. There's probably still a draw from the quick money in drugs. But the openness of the drug culture isn't nearly as prevalent. His expectations are different; he expects a clean street and to have to go looking if he really wants trouble (though maybe not as hard as others). His chances of improving himself or of just living a good, solid working man's life in a decent neighborhood have increased markedly.
I'm not foolish enough to think that broken windows is a panacea. It's not. It's a long term system which, if kept in place, increases the possibility that more people can live a better life. It would need to be augmented by many things like educational opportunities and jobs, but I suspect these are things more likely after a broken windows policy has been successfully in place for several years (or at the very least would be a significant boost to them).
Of course, as I stated above, I am also pessimistic that the very necessity of such a program being long term is the reason that it will fail - we just don't seem to have the political attention span (or will) needed for such a thing.