“The sale of the Tribune Company’s newspaper assets would provide the Koch brothers a powerful and influential platform by which to promote, at both the local, state and federal level, that enactment of their anti-public pension fund policies,” the unions said in a letter to Bruce Karsh, who is president of Oaktree Capital Management and chairman of the Tribune board of directors. It said that the Koch brothers had a history of orchestrating efforts that are “anti-labor, anti-environment, anti-public education and anti-immigrant.”

The prospect that the Koch brothers, notorious in Democratic circles for their heavy financing of conservative candidates and causes, could run The Los Angeles Times has struck a nerve in this liberal corner of the country. The Times, if somewhat diminished by the cuts it has suffered over the years, remains a powerful influence in public life here and its existence is integral to the modern history of Los Angeles.

The resistance is not only here. In Chicago on Wednesday, demonstrators protested outside the headquarters of The Chicago Tribune, which is also owned by the Tribune Company, about the possibility of a Koch takeover…

“Newspapers are public trusts, and I think it is wrong for The Los Angeles Times to end up in the hands of two people who have such a pronounced rigid ideology on a whole host of issues,” Mr. Steinberg said in an interview. Mr. Pérez, in a statement, said he was “deeply concerned about media outlets being purchased to further a political agenda.”