What are the chances that Taylor even runs, and would she have any chance or effect on the campaign at all?
I think she'd be a decent candidate to challenge Sherrod Brown if she doesn't, though it'd be tough if Obama was still popular in 2012.
Taylor would be a speed bump to Portman, but nothing more. Portman has complete establishment support and a wide and deep fundraising network. He also has no major political vulnerabilities for Taylor to exploit. In an actual primary, I would expect Portman to win around 65-30 with 5% scattering if not better.
Will she actually run? Probably not; she'll announce she's not running some time in the fall or winter as it becomes clear that she is simply uncompetitive in all primary polls.