“Mitt Romney is the person we need to lead our country,” said Miller in a statement. “Throughout this primary process the voters have vetted each candidate and after a spirited contest they have made clear who they believe is right person to lead our ticket and that is Governor Mitt Romney.  I believe they have come to this conclusion because they know that Governor Romney will begin working on day one to turn around our economy."

In Miller, Romney has won the support of a five-term congresswoman who sits on the House's Homeland Security and Transportation and Infrastructure committees.

The announcements come as Romney's staff has signaled their hope to put behind them a bruising GOP primary and shift instead to the general-election campaign.

Romney adviser Eric Fehrnstrom noted that Romney had dropped out by this point in the 2008 campaign during a Tuesday appearance on CNN.

"At the time, John McCainJohn Sidney McCainPublisher announces McSally book planned for May release Democrats lead Trump by wide margins in Minnesota Here's what to watch this week on impeachment MORE did not have the delegates he needed to clinch the nomination but he was clearly on a path to doing that. The math was very challenging for Mitt Romney. And he made the decision that at that time, the country being at war in Iraq, it was important for John McCain to begin to rally the party behind him so he could prepare himself for the fall election campaign," Fehrnstrom said.

Although he stopped short of calling on Rick Santorum and Newt Gingrich to drop out of the race, he strongly suggested it would be the right thing to do.

"These are both decent, honorable men who have run good campaigns. They are good Americans. They are good Republicans. And ultimately, I’m confident they’ll make a decision that’s not only right for their party, but right for them," Fehrnstrom said.