Democrat Barack Obama leads Republican John McCain in six of eight key battleground states one day before the U.S. election, including the big prizes of Florida and Ohio, according to a series of Reuters/Zogby polls released on Monday.

Obama holds a 7-point edge over McCain among likely U.S. voters in a separate Reuters/C-SPAN/Zogby national tracking poll, up 1 percentage point from Sunday. The telephone poll has a margin of error of 2.9 percentage points.

Obama heads into Tuesday's voting in a comfortable position, with McCain struggling to overtake Obama's lead in every national opinion poll and to hold off his challenge in about a dozen states won by President George W. Bush in 2004.

The new state polls showed Obama with a 1-point lead in Missouri and 2-point lead in Florida, within the margin of error of 4.1 percentage points. But Obama also holds leads in Ohio, Virginia and Nevada -- all states won by Bush in 2004.

The five states where Obama is ahead have a combined 76 electoral votes. Along with states won by Democrat John Kerry in 2004, they would give Obama 328 electoral votes -- far more than the 270 needed to win the White House.