His skills in this area go back to 1993, when he got more than 120,000 African-Americans to register in Chicago. From an article way back from 1993:
None of this, of course, was accidental. The most effective minority voter registration drive in memory was the result of careful handiwork by Project Vote!, the local chapter of a not-for-profit national organization. "It was the most efficient campaign I have seen in my 20 years in politics," says Sam Burrell, alderman of the West Side's 29th Ward and a veteran of many registration drives.
At the head of this effort was a little-known 31-year-old African-American lawyer, community organizer, and writer: Barack Obama. The son of a black Kenyan political activist and a white American anthropologist, Obama was born in Hawaii, received a degree in political science and English literature from Columbia University, and, in 1990, became the first black editor of the Harvard Law Review. In 1984, after Columbia but before Harvard, Obama moved to Chicago. "I came because of Harold Washington," he says. "I wanted to do community organizing, and I couldn't think of a better city than one as energized and hopeful as Chicago was then." <...>By 1991, when Obama, law degree in hand, returned to Chicago to work on a book about race relations-having turned his back on the Supreme Court clerkship that is almost a given for the law review's top editor-black voter registration and turnout in the city were at their lowest points since record keeping began.
Six months after he took the helm of Chicago's Project Vote!, those conditions had been reversed.
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To understand the full implications of Obama's effort, you first need to understand how voter registration often has worked in Chicago. The Regular Democratic Party spearheaded most drives, doing so using one primary motivator: money. The party would offer bounties to registrars for every new voter they signed up (typically a dollar per registration). The campaigns did produce new voters. "But bounty systems don't really promote participation," says David Orr, the Cook County clerk, whose office is responsible for voter registration efforts in the Cook County suburbs. "When the money dries up, the voters drop out." Nor did the Democratic Party always vigorously push registration among minorities, Orr says. "It's not that they discouraged it. They just never worked hard to ensure it would happen."
All of that changed with the ascension of Harold Washington. In the months just prior to his 1983 Democratic primary win, 120,000 new black voters were registered, most by registrars who received no bounty.
http://www.chicagomag.com/Chicago-Magazine/January-1993/Vote-of-Confidence/