From the Onion, via Marc Andreesen:

CHARLESTON, SC—After spending two months accompanying his wife, Hillary, on the campaign trail, former president Bill Clinton announced Monday that he is joining the 2008 presidential race, saying he "could no longer resist the urge."

...

Clinton also noted that, if elected, the timing would be perfect for his family, as his wife has recently expressed a desire to move back to the D.C. area.