It has been a rough few weeks for “The NewsHour with Jim Lehrer” on PBS.

In late April, Mr. Lehrer, who turns 74 on Monday, had aortic valve replacement surgery. He said he was recovering nicely and expects to be back on the air toward the end of June. But the nightly newscast’s funding situation could take longer to heal.

In its 25 years on the air, “NewsHour” has had fallow budget periods, but none that equal the current one, Mr. Lehrer acknowledged. The financial squeeze was precipitated last summer when Archer Daniels Midland ended its 14-year sponsorship of the program. That sponsorship provided nearly $4 million (and some years as much as $7 million) of the program’s yearly budget, which varies from $26 million to $28 million.

On May 1, salaries were frozen at the newscast, and company contributions to 401(k) retirement funds were suspended, cutbacks suggested by the staff. “NewsHour” still has two corporate sponsors  Chevron and the Pacific Life Insurance Company  and it receives support from PBS and the Corporation for Public Broadcasting. But only part of the Archer money has been replaced, leaving the budget several million dollars short.

“NewsHour,” along with other PBS mainstays, may have a longer-term problem. Not only are corporations cutting back on all forms of advertising during the current economic slowdown, but public television’s model  soliciting long-term commitments  is also increasingly out of step with the changing needs of corporations, which no longer sponsor public television programs for purely philanthropic reasons.