Update Saturday 6:17 am ET: The Romney campaign has officially announced through a press release that Rep. Paul Ryan of Wisconsin will be Mitt Romney's vice presidential running mate.
Sonic Boom (via NBC News):
Campaign sources indicate that Rep. Paul Ryan of Wisconsin is Mitt Romney's vice presidential pick, NBC News reported Friday night. Earlier Romney's campaign said in a statement that it would announce a running mate at 9 a.m. ET Saturday morning in Norfolk, Va., just before he begins a four-day bus tour in the battleground state.