Democrat Barack Obama leads Republican John McCain in five of eight key battleground states as Americans prepare to vote in the White House race, according to a series of Reuters/Zogby polls released on Tuesday. Obama expanded his national lead to 11 points over McCain among likely U.S. voters in a separate Reuters/C-SPAN/Zogby tracking poll, up from 7 points on Sunday. The telephone poll has a margin of error of 2.9 percentage points. Obama appeared to be firmly in command of the presidential battle as Americans head to the polls on Tuesday, with McCain struggling to beat back a challenge from Obama in about a dozen states won by President George W. Bush in 2004. The new state surveys showed Obama with a slim 1-point lead in Florida and 2-point edge in Ohio, within the margin of error of 4.1 percentage points. Obama had bigger leads in Virginia and Nevada.