Today it was Paul Ryan in Janesville, Wisconsin.
Yesterday, it was Sen. Rob Portman in Ohio.
And Saturday it was Tim Pawlenty in Pennsylvania, one day before the former Minnesota governor made the case for Mitt Romney over President Obama on ABC's This Week.
The Romney campaign has labeled this current bus trip through the Midwest the "Every Town Counts" Tour, but political analysts are calling it the Vice Presidential Tryout Tour.
With some of the possible VP picks joining Romney on the stump, observers are looking for any hint the governor might give as to who might be his No. 2.
Pawlenty appears to be in the running, despite his poor showing in the race for president.
Professor Steven Schier says Joe Biden proved you can fail at one but succeed at the other.
"You have to be on-message, a credible spokesperson, and you have to be an effective attack dog," Schier said. "Biden was all of those things in 2008 for the Dems and T-Paw has to show he can do that for the Republicans if he wants to be the vice presidential nominee."
How about Rep. Paul Ryan of Wisconsin, author of the controversial budget plan Newt Gingrich called right wing social engineering?
"I think Paul Ryan is too controversial and too obscure," Schier said.
Florida Sen. Marco Rubio is often mentioned as a frontrunner, followed by governors Chris Christie (New Jersey) and Bobby Jindal (Louisiana), and Sen. John Thune of South Dakota.
Schier says Romney's VP pick will likely be the anti-Sarah Palin, someone safe and reliable who will keep the focus on the record of the president, not raise questions about the choices of the challenger.
"For the Romney campaign, to quote Holiday Inn, the best surprise is no surprise," Schier said. "They're going to be looking for a reliable candidate who reassures people."
Romney is also reportedly looking for a candidate who is ready to be president on day one, putting a premium on experience. There is also the possibility the decision could come as soon as next month, giving the Romney campaign another key fundraiser and another critic of the president well ahead of the fall campaign.