Agriculture Committee leaders from both chambers commonly say farm policy is not a partisan issue.
Historically, disputes have split along regional lines that pit cotton and rice growers from the South against corn and soybean farmers of the Midwest. Republicans and Democrats cooperate based more on geography than party affiliation.
On food stamps, party identification increasingly appears paramount, however.
While Senate Agriculture Committee members Roberts and Thune, from the socially conservative Great Plains, want to cut food stamps, another committee member, Democrat Kirsten Gillibrand of New York, circulated a letter opposing any cuts in food stamps. It was signed by 32 Democratic senators.
In the House, Massachusetts Democrat Jim McGovern has sponsored a resolution opposing against food stamp cuts. As of Wednesday, it had 115 sponsors, all Democrats.
The farm bill died in the House at the end of 2012 in an election-year deadlock over food stamps. The Democratic-led Senate passed its version over the summer.
Small-farm activist Ferd Hoefner, policy director at the National Sustainable Agriculture Coalition, said the quarrel over SNAP could rupture a long-standing partnership of rural and urban lawmakers who supported farm programs on the one hand, and public nutrition programs on the other.
"Is this the end of the farm bill coalition?" Hoefner said.