Mitt Romney's choice for running mate is Wisconsin Rep. Paul Ryan.

That's according to a Republican with knowledge of the situation.

Romney and Ryan are to appear together Saturday in Norfolk, Va., at the start of a four-state bus tour to introduce the GOP ticket to the nation.  The campaign isn't commenting about Ryan, only saying that there will be an announcement at 9 a.m. EDT at the Nauticus Museum.  Berthed at the museum is the USS Wisconsin - which offered a hint about Romney's choice.

In the final hours before Romney's team issued the statement, all signs seemed to point to Ryan.  The seven-term Wisconsin congressman is a favorite of some conservatives.  Ryan heads the House Budget Committee and is author of a House-passed budget that would slash federal spending and overhaul entitlement programs like Social Security and Medicare.