WASHINGTON: Struggling newspapers should be allowed to operate as nonprofits similar to public broadcasting stations, Sen. Benjamin L. Cardin proposed Tuesday. He introduced a bill that would allow newspapers to choose tax-exempt status. They would no longer be able to make political endorsements, but could report on all issues, including political campaigns. Advertising and subscription revenue would be tax-exempt, and contributions to support coverage could be tax-deductible. The Maryland Democrat said the bill is aimed at preserving local newspapers, not large newspaper conglomerates.