One aspect of 2008 election race which has slipped all our notice is that this time irrespective of whether Obama or Clinton is the nominee for the Democrats that this is going to be the first election in which the candidates are members of the Senate. None of the main candidates of the main parties (McCain, Clinton, Obama) has ever served in a executive position before whether as Governor, President or VP.
It has been said that it is particularly hard for members of the Senate to run and win as they tend to have voting records with which their opponents can bash them over the head with along with a Governor/President/Veep being able to claim exclusive credit for initiative X
I'm going to check it out in more detail but so far I'm back in the 1800s and still no similar race in sight.
Update: back to McKinley in 1896 so far and can't find a Senator vs. Senator contest.
Update further: Yesterday evening I went all the way back and could not find a Presidential general election which was contested by two members of the Senate. So yep this is a first.