It seems a rare act of civic sacrifice: in the name of deficit reduction, lawmakers from both parties are calling for the end of a longstanding agricultural subsidy that puts about $5 billion a year in the pockets of their farmer constituents. Even major farm groups are accepting the move, saying that with farmers poised to reap bumper profits, they must do their part.

But in the same breath, the lawmakers and their farm lobby allies are seeking to send most of that money — under a new name — straight back to the same farmers, with most of the benefits going to large farms that grow commodity crops like corn, soybeans, wheat and cotton. In essence, lawmakers would replace one subsidy with a new one.

“We are very much aware of the budgetary constraints of the federal government,” said Garry Niemeyer, an Illinois farmer who is president of the National Corn Growers Association. “We want to do our part as corn growers to help resolve those issues, but we only want to do our proportional part. We don’t want to have everything taken out on us.”

But Vincent H. Smith, a professor of farm economics at Montana State University, called the maneuver a bait and switch.