Associated Press

Mitt Romney had a good week in terms of endorsements, snapping up the support of former President George H.W. Bush, tea party favorites Sen. Marco Rubio, R-Fla. and Sen. Mike Lee, R-Utah and House Budget Chairman Rep. Paul Ryan, R-Wis. Having already gained the support of other Republican leaders like former Utah Gov. Jon Huntsman Jr., former Wisconsin Gov. Tim pawlenty, Former Vie President Dan Quayle, New Jersey Gov. Chris Christie and South Carolina Gov. Nikki Haley, Romney still has a few GOP heavyweights who have yet to throw their support behind him. Here is the list, according to The Atlantic Wire: (See a full list of Romney's current endorsements on Wikipedia.org)

Sarah Palin
Associated Press

Palin supported Gingrich before the January South Carolina primary, saying she would vote for him to continue the GOP nominating fight, and she recently told Greta Van Susteren of Fox News that she believes Santorum could still be the Republican nominee. However, no formal endorsement has been given.

George W. Bush
Associated Press

While Romney picked up his father's support, America's 43rd president was "hard to find," Associated Press reporter Steve Peoples wrote. For now, George W. Bush's spokesman Freddy Ford said Bush is staying out of the endorsement process. Former Florida Gov. Jeb Bush, George's younger brother, endorsed Romney after Romney's victory in the Illinois primary.

Mitch Daniels
Associated Press

Although once touted as a possible contender in the 2012 presidential election, Indiana Gov. Mitch Daniels said he doesn't plan to endorse before Indiana's May 8 primary. "Well, I keep saying, 'Who the heck cares what I [think]?' I don't think anybody cares," he told the Washington Post.

Michele Bachmann
Associated Press

Rep. Michele Bachmann, R-Minn., a former presidential candidate, said in February that she would focus on being a "unifying voice" for the country, but so far she hasn't endorsed anyone for the election. She told CNN she would endorse when the time is right. "I will back whoever the people choose," she said. "But I think it's important for us to unify and unify quickly."

Rand Paul
Associated Press

Although the Senator's dad, Ron Paul, is still in the race, amid ongoing reports of collusion between the Paul-Romney campaigns, Rand Paul's name has been floating around as a possible VP pick. Rand has said that it would be an honor to be considered for such a position, but nothing official has been announced. The Washington Post lists Rand as one of the possible next big endorsements for Romney.

Jim DeMint
Associated Press

Sen. DeMint, R-S.C., announced in January that he would not endorse a candidate, but that all of them are "far superior" to President Barack Obama. During a Thursday interview with The Washington Examiner, DeMint praised Romney, but stopped short of a full endorsement. DeMint said Romney is instinctively a problem solver, and has developed the second language of conservatism.

Susana Martinez
Associated Press

The nation's only Latina governor, Susana Martinez, R-N.M., said in December that she intends to let the primary process "play itself out and let the voters decide." Romney mentioned her name when discussing possible vice presidential candidates in January, but Martinez said her job is in New Mexico.

Haley Barbour
Associated Press

The Mississippi governor may have nixed the possibility of running for president himself, and he may have voted for Newt Gingirch during his state's primary, but Barbour told NBC's "Meet the Press" on Sunday that Romney was the nominee unless he "steps on a land mine." He also recently told Bloomberg that Romney is "finally a real front-runner."