(CBS News) -- Ohio Sen. Rob Portman may not be exciting or charismatic, but that just might be why he gets the nod to be Mitt Romney's pick to run with him against President Obama and Vice President Joe Biden.
"Everything I know about Rob Portman, everything I know about Mitt Romney and the way he makes decisions tells me it's going to be Rob Portman because it emphasizes the central message of the campaign... he's not exciting, but he's well vetted," said Major Garrett, reporter at National Journal.
"And I think the essence of Mitt Romney's message is, I'm an acceptable, credible alternative and Rob Portman fills the bill," Garrett added.
Romney won five more states Tuesday night and is now focused on the general election against Mr. Obama even as he continues to amass enough delegates to become his party's nominee.
Garrett said that picking a more charismatic figure than Portman could actually be detrimental to Romney because it would just reinforce the notion that Romney is stiff and boring.
"You can't graft charisma onto an uncharismatic front-runner," Garrett said.
The former CNN and Fox News correspondent said Romney will make the case that he is an acceptable alternative to Mr. Obama and both he and Portman pass the credibility test of being able to do the job from Day One.