It is clear to all observers that the election for Romney is coming down to Ohio ( plus one other currently blue polling state e.g. Colorado) .
As is well known, no Republican has won the White House without winning that state, and although there are paths to 270 Electoral College votes for Romney without it, they are of the "run the board" type. Or as James Carville said of John Kerry's chances on election night 2004 as the evening went west (literally and figuratively) for Kerry "he would have to draw an inside straight".
If Romney loses Ohio by a small margin, even with him winning Florida, (and Virginia), it is unlikely he will be elected. One then can speculate what the difference it would have made if Ohio Senator Rob Portman had been chosen as his running mate, and had spent the entire campaign in in his home state putting the GOP's case with local knowledge and appeal.
Paul Ryan was chosen as running mate, apparently to shore up the Tea Party, Palin-ite, conservative wing who were suspicious of Romney's conservative bona fides. As things have turned out the Evangelical wing of the party has decided that "anyone but Obama" is more important than Romney's past history and they can attend to him if he backslides as president once Obama is gone.
That being the case, and the first debate seems to have been the crucial turning point which decided conservatives that Romney had a chance, they went from considering not voting to very much intending to vote. In that scenario it didn't matter who the VP candidate was as that was an entirely secondary consideration to getting President Obama out-that Ryan is a conservative was just a bonus but hardly the deciding factor.
Thus if Portman had been chosen the "Ryan bump" would not perhaps have happened. However, the bump disappeared very quickly, and the talk then turned to perhaps Ryan might cost Romney Florida by scaring the elderly. With Florida being a close race if it is lost because of Ryan's Medicare position, then the election is lost for the GOP and Ohio won't matter.
But if Romney wins Florida, and loses Ohio, when Portman might have made that small bit of voting support difference, it will be the fault of the Romney support team.
The GOP establishment will have made it two loses in a row, 2008 by backstabbing Palin and 2012 by choosing the wrong running mate. It will be high time for their dismissal for the 2016 campaign which will be the only positive out a disaster of their own making should it take place.