8 Questions

Dan Balz on topics that will shape the 2012 campaign in the final 100 days

Question 2: Will Romney's choice of a vice presidential running mate make any difference?

This is the next big moment for Romney. Once he returns from his overseas trip, vice presidential speculation will become the dominant theme of the campaign coverage until a decision is announced.

In the short term, Romney's decision will be important. His choice will say something about Romney and what message he wants to send about his candidacy. The process of picking the running mate will be the first thing he does that will be looked at in the context of presidential decision making.

But what impact will it have? Would Sen. Rob Portman of Ohio deliver his state in November? Would former Minnesota governor Tim Pawlenty put his state in play -- or help elsewhere in the upper Midwest? Would Sen. Marco Rubio energize non-Cuban Hispanic voters in Florida and beyond? Is an out-of-box pick too risky after Sarah Palin?

William Mayer, a political scientist at Northeastern University, said the likeliest way Romney's choice could make a difference is if he picks someone widely judged not to be ready to become president. Picking someone to help with a particular group of voters, he said, likely would fall flat. A swing-state running mate, however, might add votes in that state.

But in the end, Romney's choice might not make much difference. Mayer believes that Dan Quayle cost George H.W. Bush votes in 1988, but if a troubled introduction of a vice presidential running mate mattered, Bush wouldn't have been elected that year.