The latest Rasmussen Reports survey of likely voters indicated Cain got 43 percent support to Obama's 41 percent. Eight percent said they prefer another candidate and another 8 percent said they were undecided.
Cain, a Georgia businessman, is the only Republican with an edge of any kind over Obama, although former Massachusetts Gov. Mitt Romney held a similar advantage in several Rasmussen Report surveys. In the latest survey, Romney trails Obama by 2 percentage points.
"Cain now has the chance to make the case for why he should be the challenger to Mitt Romney," Rasmussen Reports President Scott Rasmussen said in a release. "Many others have auditioned for the role and fallen flat, and it remains to be seen whether Cain's fate will be similar."
Results are based on a nationwide telephone survey of 1,000 likely voters conducted Friday and Saturday. The margin of error is 3 percentage points.