1. The polls may be wrong. This is an unprecedented election. No one knows how racism may affect what voters tell pollsters—or what they do in the voting booth. And the polls are narrowing anyway. In the last few days, John McCain has gained ground in most national polls, as his campaign has gone even more negative.
2. Dirty tricks. Republicans are already illegally purging voters from the rolls in some states. They're whipping up hysteria over ACORN to justify more challenges to new voters. Misleading flyers about the voting process have started appearing in black neighborhoods. And of course, many counties still use unsecure voting machines.
3. October surprise. In politics, 15 days is a long time. The next McCain smear could dominate the news for a week. There could be a crisis with Iran, or Bin Laden could release another tape, or worse.
4. Those who forget history... In 2000, Al Gore won the popular vote after trailing by seven points in the final days of the race. In 1980, Reagan was eight points down in the polls in late October and came back to win. Races can shift—fast!
5. Landslide. Even with Barack Obama in the White House, passing universal health care and a new clean-energy policy is going to be hard. Insurance, drug and oil companies will fight us every step of the way. We need the kind of landslide that will give Barack a huge mandate.