Decision to move Ohio, Pa. races from "lean Republican" is mainly due to overall political environment, Cook analyst Jennifer Duffy says on website. Says incumbent Sens. Rob Portman of Ohio and Pat Toomey of Pa. won their seats in a "very good" Republican year in 2010; now they face re-election in a presidential year in states that President Barack Obama carried in 2008 and 2012 Says both could be hurt if Donald Trump wins GOP presidential nomination "If Trump proves to be a serious drag on the
Source: Bloomberg Politics