A campaign sticker for Republican presidential candidate Mitt Romney is seen on a sign for Romney Street in London on Wednesday, as Romney arrived to meet with leaders, hold fundraisers and attend the opening of the Olympics. Charles Dharapak/AP hide caption

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Mitt Romney speaks at a campaign event in Bow, N.H., Friday. The campaigns have released their monthly financial reports, with Romney showing an advantage over President Obama. Charles Dharapak/AP hide caption

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Karen Bleier /AFP/Getty Images

Montana Attorney General Steve Bullock sought to prevent the U.S. Supreme Court's 2010 Citizens United decision from being used to strike down a state law restricting corporate campaign spending. On Monday, the Supreme Court rejected Bullock's argument, holding that "there can be no serious doubt" that Citizens United applies to Montana law. Matthew Brown/AP hide caption

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Justice Anthony Kennedy, who wrote the Citizens United opinion saying that corporations can pay for ads expressly promoting or attacking political candidates. Chip Somodevilla/Getty Images hide caption

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Screen grabs of four separate ads from four different political groups critical of President Obama's handling of Solyndra, the failed solar-panel maker. Clockwise from top left, the ads are from: Americans for Prosperity, MittRomney.com, American Crossroads and Crossroads GPS. hide caption

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Bill Koch (center) celebrates his team's 1992 America's Cup win. Koch, the brother of billionaire GOP donors Charles and David, has given $2 million to the superPAC backing Mitt Romney. Vince Bucci/AFP/Getty Images hide caption

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