Who will Mitt Romney pick to be his running mate? His six-state bus tour is fanning more speculation, especially about Ohio Senator Rob Portman.
The up and down odds on running Mitt Romney's possible running mates are keeping political gamblers and guessers busy.
Romney's bus tour is proving to be a test drive of sorts for some could-be contenders.
Senator Rob Portman shared the stage in Brunswick and other Ohio stops.
A couple of others also got bus tour spotlight tryouts -- former Minnesota Governor Tim Pawlenty was with Portman in Pennsylvania, Wisconsin Congressman Paul Ryan was the warm up act at stops there.
What kind of person does Romney want next to him?
It's believed his priorities are someone ready to be president right away and someone who is all-in in the campaign.
His staff's believed to be vetting every prospect's public votes, public statements, public writings and family histories.
Portman's style is not the most dynamic, even boring some think.
Some say Florida Senator Mario Rubio and Louisiana Governor Bobby Jindal and New Jersey's Chris Christie would bring more excitement, energy and charisma.
Most observers believe Romney won't go for a Sarah Palin wild card.
Romney took a state from deficit to debt to surplus.
Portman's stock answer is he's got an important role to play in the Senate. He served President George Bush, which might be election baggage.
But many Republicans donors like him and consider him a safe if serious bet.