In 1999, a state senator from Chicago heard constituents complain that police were free to pull over drivers because they were black.
So Barack Obama proposed a bill to tackle racial profiling. When it failed, he revised it and proposed it again and again.
"Race and ethnicity is not an indicator of criminal activity," Obama said when his bill finally passed the Illinois state Senate four years later.
He said targeting individuals based on race was humiliating and fostered contempt in black communities.
His efforts offer some of the clearest clues as to how the first black US president feels about an issue that's polarizing a nation upset by the shooting death of unarmed black teenager Trayvon Martin.
Obama has rarely spoken about his own experience with incidents he perceived to be race-related. In his 2006 book The Audacity of Hope, he described his struggles with the injustices of "driving while black" and the vigilance he felt was still necessary for him and his family.
"I can recite the usual litany of petty slights that during my 45 years have been directed my way: security guards tailing me as I shop in department stores, white couples who toss me their car keys as I stand outside a restaurant waiting for the valet, police cars pulling me over for no apparent reason," Obama wrote.
Obama's administration has treated carefully the acquittal of George Zimmerman, the neighbourhood watch volunteer who fatally shot Martin during a confrontation in his Florida gated community, where Martin was visiting family.
Hurt in the past by injecting himself into racial debates, Obama is wary of taking sides this time. After Zimmerman's acquittal, an Obama statement said "a jury has spoken," and he called for calm.
While Martin's family has said the teenager was racially profiled, race was barely mentioned during the nationally televised trial.
Now the Justice Department is looking into Martin's death to see whether civil rights charges can be filed.
Federal prosecutors would have to show evidence Zimmerman was motivated by racial animosity to kill the 17-year-old.
Zimmerman says Martin physically assaulted him and he shot the teenager in self-defence.
Obama, in his only public comments on the verdict, looked to the future, urging Americans to ask themselves how such tragedies can be prevented.
These days, he cites gun control. But as a young state senator, he and a few colleagues led a fight to require police to keep track of the demographics of drivers they pulled over - race, gender and age - then have those records analyzed to root out any patterns of bias.
Another bill Obama pushed sought to prevent wrongful convictions by requiring police to videotape interrogations for crimes like homicide.
"There was strong opposition from law enforcement on these issues," Emil Jones Jr., the state Senate's president at the time, said in an interview. "He was skillful enough to be able to get them on board."
One of Obama's arguments to skeptical police groups was to say his legislation could actually exonerate fair-minded officers. Those unjustly accused of racial profiling would have evidence to show that wasn't the case.
Both the racial profiling and videotaped interrogations bills eventually passed in the Legislature in 2003.
When the profiling bill became law, the data showed blacks and other minorities were being pulled over about three times as often as whites, said Craig Futterman, who sits on the statewide panel that oversees the law. These days, it's down to about twice as often, he said.
"The fact that this data was being collected and monitored actually dramatically reduced racial profiling in Illinois," said Futterman, a professor at the University of Chicago Law School, where Obama once taught.
But as rallies continue across the US, with protesters demanding justice for the teenager who was shot dead after buying candy, it's not clear what steps the administration may take.
"I don't have any process to announce today going forward," said Jay Carney, Obama's spokesman.
He noted Obama's work on the issue in Illinois and said Obama "believes it's an issue worthy of consideration and action."