As the Presidential race tightens and Hurricane Sandy whips the country into a frenzy only one week before the election, it's becoming very clear that the key state this year will be .... OHIO. Both parties will pour many more millions into Ohio advertising over the coming week, but clearly the outcome will remain uncertain until election day. Obama is currently showing a slight lead based on polling averages at RealClearPolitics.com, but some polls such as Rasmussen show Romney now leading (though Rasmussen does tend to skew Republican).
Without Ohio no Republican has won the white house, and it's unlikely that Romney could be the exception to this rule. If Ohio goes Obama then Mitt Romney would have to win *every other battleground state* to win, and that outcome is very unlikely.
In fact current polling generally shows Obama winning the election by electoral votes while *losing* the popular vote. This is a rare occurrence but as you recall it happened in 2000 when GW Bush beat Al Gore by electoral votes while losing the national popular vote by about 500,000.
Turnout will also be a critical factor. Incredibly, it's entirely possible that a bright sunny Nov 6 in Ohio will give the election to Obama while a rainy cold day will push it to Mitt Romney.