Bush beat Kerry in 2004 in Ohio with Kerry winning Cuyahoga by 448K to 222K. Obama won Cuyahoga in 2008 458K to 200K (note the lower vote total, which I assume is due to population decline, total 2-party vote in Ohio was pretty much the same in 2004 and 2008).
If Romney's within 100K in Cuyahoga, he wins Ohio going away. But that isn't going to happen. If he keeps it to 220K or under, that's a good sign because that parallels what happened in 2004, when Bush won the state.
But I think the key to all this isn't percentage, it's turnout. Obama's going to win Cuyahoga by something close to 2-1. It's how many people vote there that's the key, because that will have a huge influence on the margin. That's why I would be curious to see a comparison, by mid-day, of early votes plus turnout thus far in Cuyahoga as compared to 2008. I don't know if that sort of information is available, but it could be telling.
I am in Southern Montgomery County (Republican area even though Dayton is a Democratic hell hole) and it was the largest voting line I have ever seen. I bet it was an hour wait. In fact, it was so crowded that I left and will return to vote after lunchtime. I think this is a good sign!!
BTW -
I wish we could give Cleveland to Canada! F-in liberals!