A couple of things.
First...her sexual orientation has ONLY been a point of consideration because of HER declarations. She has run for and won some form of political office in Oregon for over 20 years now and no one has cared.
Second...I think bisexuality is far more commonly accepted than homosexuality. Bisexual people tend to present as more 'normal' (pull back the claws...not making a judgment...stating fact). In women, I dont think people find it all that upsetting or shocking. In men...well...once you get past the automatic negative response associated w/ man on man equals less of a man...you are back to 'but its not that big of a deal'.
Third...Bisexuality kinda works both sides of the 'born that way' and/or 'we can choose our sexuality' argument.
At the end of the day...its an Oregon thing...and people from Oregon have supported her for 20+ years.
From a guys perspective...I hope her girlfriend is hot!