Perhaps but Hagel has been more centrist than most of the GOP, and has been vocal in his criticism of Bush, so I think he would be palatable to most democrats. And It would show a difference between the parties, the willingness of the dems to work with Republicans unlike the GOP, McCain would never take on a Dem VP.
As for assasination, it's a risk whether or not he picks a republican VP, but you can't live in fear over those type of things, have hope 
Predictions:Sales of Wii Fit will surpass the combined sales of the Grand Theft Auto franchiseLifetime sales of Wii will surpass the combined sales of the entire Playstation family of consoles by 12/31/2015 Wii hardware sales will surpass the total hardware sales of the PS2 by 12/31/2010 Wii will have 50% marketshare or more by the end of 2008 (I was wrong!! It was a little over 48% only)Wii will surpass 45 Million in lifetime sales by the end of 2008 (I was wrong!! Nintendo Financials showed it fell slightly short of 45 million shipped by end of 2008)Wii will surpass 80 Million in lifetime sales by the end of 2009 (I was wrong!! Wii didn't even get to 70 Million)
