Well-conducted Ohio polls are catnip for political analysts. So here goes: a new Quinnipiac poll of the state gives President Obama his lowest job approval rating there since the beginning of his presidency, with only 45% of voters saying he's doing a good job.  At the same time, the Republican candidate for retiring Sen. George Voinovich's seat, ex-Bush administration official/ex-Rep. Rob Portman, has small leads over both his potential Democratic opponents.  The economy and the health care debate seem to be driving Ohio's voters back into the purple -- if not the red. 57% disapprove of the way Obama has handled health care reform. Self-identified independents disapprove of Obama's health care handling by nearly two-to-one.