US President Barack Obama holds a slight lead over his Republican rival, Mitt Romney, in key swing states that could determine the outcome of the 2012 presidential race, a new opinion poll found Sunday

US President Barack Obama holds a slight lead over his Republican rival, Mitt Romney, in key swing states that could determine the outcome of the 2012 presidential race, a new opinion poll found Sunday.
  
The USA Today/Gallup survey showed Obama ahead of Romney 47 percent to 45 percent among registered voters.
  
The states covered by the poll included Colorado, Florida, Iowa, Michigan, Nevada, New Hampshire, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin.
 
Swing states are usually not firmly or predictably aligned with either Democrats or Republicans and as such, in many instances can determine the outcome of national races.
  
In the rest of the country, Obama led Romney 48 percent to 44 percent, according to the survey. The poll of 2,404 registered voters was conducted June 22-29 and had a margin of sampling error of plus or minus four percentage points.