U.S. House leadership notched a rare victory last week over the capital’s conservative pressure groups and their quest to yank Republicans to the right.

The narrow vote to pass half of a Farm Bill – and the hyperpartisan debate it sparked – were still evidence of the groups’ impact, and the question remains how often Republicans will want to pick this food fight.

Count Coweta County Republican Rep. Lynn Westmoreland among the ones who have had quite enough. He openly accused Heritage Action for America, the advocacy arm of the conservative Heritage Foundation think tank, of “losing … credibility” because of its approach to the bill.

Such things usually stay off the record up here. The comment was a sign of Westmoreland’s candor and his frustration.

Heritage Action, FreedomWorks, Americans For Prosperity and the Club For Growth are among the groups that track votes, score legislators and try to bring the forces of the right to bear on Republicans. This usually involves a primary threat.

The Farm Bill is one of their prime targets. It’s an expensive five-year package of farm subsidies and nutrition programs such as food stamps.

The Senate version, which eliminated direct federal payments to farmers in favor of risk-management programs and barely dinged food stamps, passed easily. The House version, with less cuts to farmers and more squeezes on food stamp eligibility, failed on the floor and embarrassed House leaders. Democrats mostly abandoned the bipartisan-crafted bill after more food stamp restrictions were added in a floor amendment.

The amendment was one of the “key votes” from Heritage. So was the final bill, which Westmoreland voted for against Heritage’s wishes.

“The next morning we all woke up to emails sent out to our constituents in our district talking about how sorry we were and how, you know, terrible people we were,” Westmoreland said. “One hundred and nine of the [conservative Republican Study Committee] members voted for it. These are the people that’s their stronghold. So once you do something like that, you kind of lose your credibility up here.”

The reply from Heritage Action’s Dan Holler: “It sounds like Mr. Westmoreland and his staff had good, productive conversations with people of Georgia’s third district, and those policy conversations are the key to accountability and transparency in government.”

Heritage and its brethren sought what finally happened last week: The House split the farm and nutrition portions. But the groups still don’t like the contents of either half of the bill.

The House still passed the farm side in a narrow partisan vote. Among Georgia Republicans — many of whom draw “A” grades from the pressure groups — the only one to vote no was Rep. Phil Gingrey of Marietta, a decision no doubt made with his U.S. Senate primary in mind. (He voted for the Farm Bill in 2008.)

The next step is unclear. The House could try to conference half of the Farm Bill with the Senate’s full version. It could return with a bill that makes bigger cuts to nutrition programs than the $20.5 billion sought in the first vote.

Democrats see racial undertones in any new food stamp eligibility restrictions. Atlanta Democratic Rep. David Scott said “they have an image of lazy black folk or illegal immigrants or whatever.”

Scott declared the House farm-subsidy bill “dead on arrival over there” in the Democrat-controlled Senate because of the party-line House vote. President Barack Obama vowed a veto, too.

House Republicans remain in a Farm Bill box. The only ways out would rile up the conservative groups. But as last week proved, they don’t always win.