Obama's and Biden's ‘Senate-ness' could prove to be a disadvantage

In the 20th-century history of presidential elections, up to the present, there appears to be a built-in popular bias against U.S. senators, especially sitting senators. By naming Joseph Biden as his running mate, Barack Obama has forged a ticket of not one but two sitting senators, which has only been tried once in the past 108 years. Is that too much "Senate-ness" for the American electorate? Let us examine the extent of this bias, its possible sources, how Obama might overcome it and who McCain should choose if he wants to play the odds.