Polling expert Nate Silver (cited in an earlier post) says the most likely electoral maps that would give a win to McCain all put Ohio in his column.
Silver conducts his projections by using poll numbers to run 10,000 simulations of the election. Here's how he described Ohio's place in the simulations:
Also, there are some states that truly do appear to be "must-wins" for McCain. In each and every one of the 624 victory scenarios that the simulation found for him this afternoon, McCain won Florida, Georgia, Missouri, Indiana and Montana. He also picked up Ohio in 621 out of the 624 simulations, and North Carolina in 622 out of 624. If McCain drops any of those states, it's pretty much over.Read his entire post