THE DETAILS OF federal food and agriculture policy have always been notoriously complex. The politics, though, have not.

Every five years Congress passed a farm bill that represented a deal between urban and rural states. The city folk got food stamps to help the urban poor (and the grocery chains that sell to them) and the rural folk got subsidies for commodity producers, as well as the boost in demand from food stamps. A few urban reformers would ritualistically protest handouts to wealthy farmers; a few rural conservatives would protest handouts to the dependent poor. But, in the end, a deal got done.

That’s starting to change. The rise of a Republican-majority House tilted toward the tea party, coupled with the doubling of food-stamp spending since the Great Recession, has set off a movement to curtail that $80 billion-a-year program. The House Agriculture Committee’s proposed renewal of the farm bill includes a $20 billion food-stamp cut over the next 10 years. “We represent the people’s money, and we have to be good stewards of that,” said committee member Rep. Stephen Fincher (R-Tenn.). Never mind that Mr. Fincher received a $70,000 farm subsidy in 2012, according to the Environmental Working Group. (Through a spokeswoman, Mr. Fincher declined comment.)

Meanwhile, members of both parties are looking for ways to reduce deficits, and subsidies for agribusinesses that are booming as never before are a logical place to start. President Obama’s 2014 budget proposal trimmed agriculture by $37.8 billion over 10 years.

In fairness, the bill for which Mr. Fincher voted echoed Mr. Obama’s proposal to some extent, ending the $3 billion-a-year direct payment program from which the congressman benefited. However, it would install a deeply subsidized crop insurance program that could cost even more — and create all sorts of market distortions.

Expanded subsidized crop insurance is also the centerpiece of the farm bill moving through the Senate, which contains only $4.1 billion in food-stamp reductions. Parts of the Senate bill do count as reform, relatively speaking: Crop insurance subsidies are limited for farmers making more than $750,000; farmers who take insurance must participate in soil conservation.

In the end, Congress may fail to pass a bill due to differences between the House and Senate over how much to cut food stamps. That happened last year; as a result, the country is operating under a one-year extension of the old law.

Old Washington hands may take another farm bill failure as a sign of dysfunction, but what’s really dysfunctional is dealing with these issues through interest-group logrolling rather than on their merits. People can debate how much help the poor should get and whether it’s optimal to deliver aid in the form of food stamps. But it’s beyond debate — or should be — that government has a role to play in helping them. By contrast, U.S. farmers are wealthy enough to take care of themselves and have been for many years. There’s no argument — beyond the spurious specter of food shortages — for propping them up with taxpayer money. The sooner Congress starts making policy with those truths in mind, the better.