Rob Portman, 56, endorsed Romney early on and campaigned with him in Ohio, helping Romney to a narrow win in a battleground state that will be key in November. Portman is a relatively low-key but deeply experienced politician and would be seen as a safe, steady choice. But as a former budget director for President George W. Bush, Portman would be an easy target for Democrats, who could accuse him of contributing to the dire fiscal shape the government's finances are in.
Romney's VP list
The likely front-runners and long shots on Romney's short list.