

'Plus ça change, plus c'est la même chose' -
Jean-Baptiste Alphonse KarrIn the House of Representatives, 87% of the incumbents who stood for election were re-elected. This is slightly below the historical trend over the last several decades, and lower than the re-election rate in 1994, 2006, and 2008:
In the Senate, and assuming Lisa Murkowski’s write-in bid is successful, 84% of the incumbents who stood for re-election were successful (the number drops to 80%). Again, this is fairly consistent with the historical rate over the past forty years or so:

So, despite the changes that many are calling “historic,” the fact of the matter is that incumbents were, for the most part, as safe in 2010 as they have been in previous elections.
(from
outsidethebeltway.com)