A story on CNN says Senator McCain is statistically tied with Senators Clinton and Obama in Florida and Ohio, but in Pennsylvania, Senator Clinton beats Senator McCain by 6 points - these results are based on a Quinnipac poll taken Feb 6-12. So effectively, Senator Clinton has an edge in electability... or so the story goes.
However, CNN is not presenting polls taken in other swing states. For example, Rasmussen Reports has polls for New Hampshire, Colorado, Nevada, and Missouri:
Missouri (2004 Bush +7): McCain (+1, +2) tied with both Clinton and Obama
New Hampshire (2004 Kerry +1): Obama-McCain 49-36 (+13%), Clinton effectively tied 43-41 (+2)
Colorado (2004 Bush < +5): Obama-McCain 46-39 (+7%); Clinton-McCain 35-49 (-14%)
Nevada (2004 Bush): Obama-McCain 50-38 (+12%); Clinton-McCain 40-49 (-9%)
These are states which have seen Senator Obama campaign, unlike Florida, Ohio and Pennsylvania. So I think MO/NH/CO/NV are a much better indicator of swing-state electability than FL/OH/PA.
Note that Senator Clinton narrowly beat Senator Obama in Nevada and New Hampshire, while Senator Obama edged her in Missouri and handily won the caucuses in Colorado. However, the large winning margins for Senator Obama in NV/NH/CO comes from unaffiliated and Republican voters. Senator Obama draws support from these two groups, away from Senator McCain. Senator McCain may not be very popular amongst Republicans (link), but Senator Clinton definitely is - in a perverse fashion.
Bottom line - Senator Obama can definitely win swing states which Senator Clinton cannot. And in Pennsylvania, he ties McCain; with personal exposure to voters, Senator Obama could very well come away with PA as well.