Republican presidential candidate, former Massachusetts Gov. Mitt Romney addresses the Latino Coalition's 2012 Small Business Summit, Wednesday, May 23, 2012, in Washington. (AP Photo/Mary Altaffer)

FILE - In this May 21, 2012 file photo, President Barack Obama speaks at a news conference in Chicago. President Barack Obama and his party are redoubling their fundraising efforts. They're doing it in the wake of robust hauls by rival Mitt Romney and a slew of GOP-leaning super PACs that are raking in cash from Republicans highly motivated to topple the Democrat. (AP Photo/Kiichiro Sato, File)

FILE - In this Dec. 6, 2010, file photo, Harold Hamm, chief executive officer of Continental Resources Inc. of Enid, Okla., speaks during an Associated Press interview in Bismarck, N.D. Hamm didn’t wait long to make a nearly $1 million donation to a group supporting Republican presidential candidate Mitt Romney after he became one of Romney’s top energy advisers in March. Just weeks after Hamm joined the Romney campaign, he gave $985,000 to a pro-Romney super PAC, according to campaign reports. Hamm’s company, Continental Resources Inc., oversees oilfield stakes in North Dakota and Montana, and Hamm has been disdainful of President Barack Obama’s energy policies. (AP Photo/Dale Wetzel, File)