According to today's paper (here
Chicago Tribune) there was no specific event or threat that triggered the decision.
And not only Powell but Jesse Jackson got Secret Service protection from the day he announced his candidacy as well.
Quote:But white supremacists, appalled that a black candidate may have a viable shot at the presidency, have been spewing venom across the Internet for months.
"Our world will become unbearable with him as President," wrote a typical poster on a white powerWeb site. "Maybe there will be someone who would take [a] chance and do a Lincoln on him? Is that our only hope?"
[...]
An article in last week's edition of the rightwing Insight magazine blasted him for his lack of security, mentioned Robert Kennedy and accused Obama of "almost courting this tragic, and historically predictable, result."
"It is time for Obama to put aside his pride, or bravado, and ask for the protection he requires," the magazine said.
Source: New York Daily News, 04.05.07, page 7