[semantic]

It's called the Chicago Machine.

I beg to disagree - the real reason is exactly as Ferraro implied: it's due to affirmative action.

[bcsco]

Affirmative Action certainly plays a role, but the Chicago Machine is the vehicle by which Obama catapulted to the national stage. It enabled (read “engineered”) his Senate seat in the Illinois legislature, and later his ascendancy to national politics. All was accomplished through Illinois Democrat politics.