Polls apart: Why polls vary on presidential race

Barack Obama is galloping away with the presidential race. Or maybe he has a modest lead. Or maybe he and John McCain are neck and neck.

Confusing? Sure, thanks to the dueling results of recent major polls.

In the past week, most surveys have shown Democrat Obama with a significant national lead over Republican McCain. Focusing on "likely voters" _ as many polling organizations prefer this close to Election Day _ an ABC News-Washington Post survey showed Obama leading by 11 percentage points. A Wall Street Journal-NBC News poll had the same margin, while the nonpartisan Pew Research Center gave Obama a 14-point edge.

But others had the race …