WASHINGTON, March 24 (Reuters) - With many U.S. newspapers struggling to survive, a Democratic senator on Tuesday introduced a bill to help them by allowing newspaper companies to restructure as nonprofits with a variety of tax breaks.

"This may not be the optimal choice for some major newspapers or corporate media chains but it should be an option for many newspapers that are struggling to stay afloat," said Senator Benjamin Cardin.

A Cardin spokesman said the bill had yet to attract any co-sponsors, but had sparked plenty of interest within the media, which has seen plunging revenues and many journalist layoffs.

Cardin's Newspaper Revitalization Act would allow newspapers to operate as nonprofits for educational purposes under the U.S. tax code, giving them a similar status to public broadcasting companies.

Under this arrangement, newspapers would still be free to report on all issues, including political campaigns. But they would be prohibited from making political endorsements.

Advertising and subscription revenue would be tax exempt, and contributions to support news coverage or operations could be tax deductible.

Because newspaper profits have been falling in recent years, "no substantial loss of federal revenue" was expected under the legislation, Cardin's office said in a statement.

Cardin's office said his bill was aimed at preserving local and community newspapers, not conglomerates which may also own radio and TV stations. His bill would also let a non-profit buy newspapers owned by a conglomerate.

"We are losing our newspaper industry," Cardin said. "The economy has caused an immediate problem, but the business model for newspapers, based on circulation and advertising revenue, is broken, and that is a real tragedy for communities across the nation and for our democracy.

Newspaper subscriptions and advertising have shrunk dramatically in the past few years as Americans have turned more and more to the Internet or television for information.

In recent months, the Seattle Post-Intelligencer, the Rocky Mountain News, the Baltimore Examiner and the San Francisco Chronicle have ceased daily publication or announced that they may have to stop publishing.

In December the Tribune Company, which owns a number of newspapers including The Baltimore Sun, The Chicago Tribune and The Los Angeles Times filed for bankruptcy protection.

Two newspaper chains, Gannett Co Inc and Advance Publications, on Monday announced employee furloughs. It will be the second furlough this year at Gannett. (Additional reporting by Chuck Abbott) (Editing by David Storey)