They may have picked an unusually high-profile food fight with the White House — and especially the East Wing — but GOP lawmakers behind the push are confident it’s a fight they can win.

The House Appropriations Committee voted, 31-18, Thursday to advance a fiscal 2015 agriculture spending bill with a controversial rider that would allow schools to opt out of nutrition rules requiring more fruits and vegetables, less sodium and more whole grain-rich products if they are losing money from the healthier meals.

( Also on POLITICO: Panel backs school lunch waivers)

The move sets up what promises to be a contentious conference between the House and Senate bills, although the measures have yet to clear either chamber.

Rep. Robert Aderholt (R-Ala.), chairman of the House Appropriations subcommittee on agriculture, told POLITICO after the vote that he’s confident Republicans will ultimately prevail in giving school districts the option of a waiver.

“I think that between now and when we go to conference, that you’re going to hear the school nutritionists speak very loudly to [lawmakers],” said Aderholt, who predicted that some Democrats will break ranks and back the effort.

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“This is not a roll back and so I think that people, when they see what the language is, they’ll be very open to this,” Aderholt said.

But Democrats are digging in their heels, buoyed by uncharacteristically public political support from first lady and the fact that the Senate Appropriations Committee did not include the waiver in the recent approval its agriculture spending bill.

White House spokesman Jay Carney responded to the House Appropriations Committee action during the daily briefing on Thursday, calling the rider on school lunches “a provision that replaces the judgment of doctors and nutritionists with the opinions of politicians regarding what is healthy for our kids.”

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“The House Republican proposal would undercut school nutrition standards that have already been successfully implemented in over 90% of schools,” Carney said. “These are the same people who just last year declared pizza as a vegetable and who now think that decisions about kids’ health should be made by politicians instead of pediatricians.”

The Senate spending bill does not contain waiver language but includes a much more limited amendment that asks the Department of Agriculture to further study the next wave of rules that would mandate all breads, pastas and cereals be whole grain rich and set stricter limits on sodium in school meals. It also asks the department to ensure products like whole grain tortillas and biscuits are adequately available to schools.

The White House and nutrition advocates, however, view the waiver as a veiled attempt to gut the law until Congress reauthorizes child nutrition programs next year.

House Democrats vociferously fought back during the markup of the House spending bill Thursday, but failed to pass an amendment by Rep. Sam Farr (D-Calif.) to strip the waiver language from the measure. The panel rejected the amendment by a 29-22 vote.

“Congress should know better,” said Farr during the meeting. “Let’s put kids’ health first.”

“We don’t tell kids, ‘Look, you don’t have to take math if it’s hard or science if it’s hard,’” Farr said. “This opt out of nutrition is just the wrong way to go.”

Aderholt, however, strongly defended what he called “a very real problem in many school districts across the country.”

“We’ve had calls, we’ve had emails, we’ve had meetings with school nutritionists, who some of us affectionately know as lunch ladies,” he said.

Aderholt emphasized that the waiver only allows schools a one-year break on regulations “if and only if a school has lost money over a six-month period.”

In a particularly pointed exchange during markup, Rep. Debbie Wasserman Schultz (D-Fla.) asked Republicans on the committee whether they are aiming to make waivers permanent – a concern that Agriculture Secretary Tom Vilsack and others have raised in recent days.

“So the majority does not intend to eliminate these nutrition standards?” asked Wasserman Shultz.

“Not in this bill,” Aderholt said. The packed room erupted in laughter and then Aderholt noted that the waiver would only apply to the next school year.

The opposition to many of the new nutrition standards, which stem from the 2010 Healthy Hunger-Free Kids Act, has been fueled primarily by an extensive lobbying effort by the School Nutrition Association.

The group, which represents 55,000 school nutrition professionals and the food companies that supply the National School Lunch Program, has been flying in school meal directors and cafeteria workers from across the country to ask lawmakers to give schools some regulatory relief by “hitting the pause button” on the sweeping rules.

SNA argues that many schools are struggling to adjust and losing money as a result. Kids, they say, are having an especially hard time adjusting and are throwing the healthier meals in trash cans.

The bitter fight over the nutrition rules have sparked remarkably bold, political moves from the first lady. On Tuesday, Obama hosted a roundtable with school nutrition leaders who support the changes and don’t think schools should be allowed to opt out.

The first lady expressed frustration over the effort on Capitol Hill and directly questioned why SNA had changed their tune after lobbying for the landmark school lunch reform law, which cleared Congress with strong bipartisan support.

“Why are we even having this conversation?” Obama asked during the meeting with nutrition leaders Tuesday. “Help me understand why, especially given the fact that the School Nutrition Association worked to pass the original changes in the nutrition standards. … If anyone can help me understand how we wound up here …”

Several nutrition advocates have alleged that SNA’s industry members like ConAgra, Schwan’s and Domino’s are behind the pushback against stricter food standards, something SNA strongly denies.

On Wednesday morning, The New York Times ran an op-ed by the first lady, in which she called on lawmakers to listen to nutrition experts.

“The bottom line is very simple: As parents, we always put our children’s interests first,” Obama said. “We wake up every morning and go to bed every night worrying about their well-being and their futures. And when we make decisions about our kids’ health, we rely on doctors and experts who can give us accurate information based on sound science. Our leaders in Washington should do the same.”

Nutrition advocates, who have been playing defense to keep the new nutrition rules on track, expressed disappointment Thursday after the House advanced the spending bill.

The produce industry, a major backer of the new nutrition standards, which mandate more fruits and vegetables be served, chided the committee for advancing the waiver provision.

“We are deeply disappointed by the vote today by the House Appropriations Committee to roll back school meal nutrition standards that benefit the health of millions of American children,” said United Fresh President & CEO Tom Stenzel. “

Stenzel said that he believes the lengthy debate over Farr’s amendment during markup “shows that the waiver provision in the current bill is flawed.”

“If Republicans are truly concerned about children’s health and support healthy school lunches, they should constructively help schools meet nutrition standards and serve good tasting, healthy food to school children, not give schools a free pass and go back to the days of serving junk food,” said Margo Wootan, director of nutrition policy at the Center for Science in the Public Interest.

Nancy Brown, CEO of the American Heart Association, which lobbied for the school lunch reforms, blasted the appropriations vote.

“We cannot go back to the days when the answer to ‘What’s for lunch?’ was pizza, french fries and chicken nuggets,” Brown said in a statement.

“America’s school lunch program works and will help our children live free of heart disease and stroke,” Brown said. “Our urgent plea to Congress is to not undo the program’s strong progress by putting special interests back on school menus.”

SNA responded Thursday by applauding appropriators and by demanding that both USDA and the Obama administration take “immediate action” to give schools regulatory relief.

“We appreciate the House Appropriations Committee’s support for this waiver to give temporary needed relief to some schools across the country,” said Leah Schmidt, president of the group. “This will not halt the progress in school cafeterias; it is a temporary reprieve to allow schools to catch up.”