When congressional leaders earlier this month named six lawmakers from each party to a debt reduction “supercommittee,” investing unprecedented power in a tiny cadre to slash funding, they set off a wild scramble among special interest groups to gain access and protect their interests. Yet many groups with the most at stake didn’t have to change their plans. Some members of the supercommittee received more campaign contributions in July from political action committees controlled by corporations, unions and other lawmakers than anyone else in Congress, disclosures filed this weekend show. Rep. Dave Camp, Michigan Republican who chairs the tax-writing House...