A National Farmers Union rally urges Congress to pass a farm bill before expiration of the old bill on Sept. 30, 2018.

Several leading Democratic conference committee members are up for re-election this year, and some of their GOP challengers have looked to make an issue out of the farm bill standoff. Trump also has weighed in on the issue by blaming the Democrats and endorsing some of the Republican challengers.

The Senate's $428 billion farm bill passed in late June, but unlike the GOP-led House version , it didn't include additional food stamp working requirements that the Democrats are opposing. There also are differences over reductions to conservation programs and farmer payment limits in the Senate version that were introduced by Sen. Chuck Grassley, R-Iowa, but are at odds with the House version .

Duncan also said the trade war is on farmers' radar, particularly the tit-for-tat tariffs by the U.S. and China that have hit such commodities as soybeans, corn and pork. In addition, retaliatory tariffs remain in place from Mexico targeting U.S. dairy and pork as a result of President Donald Trump 's duties on imported steel and aluminum.

"We're hopeful that after the election, the sides can come together and then the House and Senate can find some common ground," said Brian Duncan, who produces corn, soybeans and pork about two hours outside Chicago and is vice president of the Illinois Farm Bureau.

The lack of progress on the legislation has frustrated some farmers and become a campaign issue in the heartland at a time when the farm economy is struggling with low commodity prices and trade retaliation.

With campaigning in the final days before Tuesday's elections, a major issue Congress will have to deal with when it returns is the stalled farm bill.

President Donald Trump holds up two hats that say 'Make Our Farmers Great Again' as he departs the White House August 30, 2018 in Washington, DC.

"I am very surprised the farm bill has been held up because the changes have been so modest from my point of view," said Chris Edwards, an economist with the Cato Institute, a think tank that describes itself as libertarian. "And with everything else going on in the agriculture world, like Trump's trade war, the lower prices for crops, you would have thought that the farmers would have put enough pressure on Congress to get it done."

Rep. Collin C. Peterson, D-MN., ranking member of the House Agriculture Committee addresses the National Farmers Union (NFU) rally to urge Congress to pass a farm bill before September 30.

In Minnesota, Rep. Collin Peterson, the Democratic ranking member of the House Agriculture Committee and co-chairman of the conference committee, is seeking a 15th term and running against Republican challenger Dave Hughes in an agriculture-laden district Trump carried by nearly 31 points in 2016.

Hughes, an Air Force veteran who lost to the incumbent in 2016 by 5 points, has sought to frame Peterson as "walking away" from the farm bill. "If he had stuck to his job and done his job, we might have a farm bill," Hughes said during a debate Oct. 19.

"We are at an impasse, and it's not because I walked away or anything like that," Peterson responded. "It wasn't me who put this stuff in the bill."

Peterson called the House's farm bill "completely partisan" and especially changes to food stamps, or the Supplemental Nutrition Assistance Program. "If you're going to get a bill done you have to get bipartisan support for it both in the House and Senate."

The House bill would change work requirements for able-bodied adults getting SNAP benefits from 20 hours a week under current rules to 25 hours week. Certain recipients are exempt from the employment requirements, including pregnant women, the elderly and disabled.

The House bill includes cuts of more than $20 billion in SNAP benefits over 10 years. The Congressional Budget Office estimated that the provisions could see about 1.2 million low-income Americans lose their benefits.

Total benefits paid out last year by SNAP exceeded $63 billion, and went to more than 42 million participants.

The White House has pushed for tougher work requirements for assistance programs that target low-income Americans, including food stamps and public housing aid.

Trump last month sought to blame Democrats and the ranking member of the Senate Agriculture Committee, Sen. Debbie Stabenow, D-Mich., for being "totally against approving the Farm Bill" and for "fighting tooth and nail to not allow our Great Farmers to get what they so richly deserve." Trump's tweet came just weeks before the 2014 Farm Bill expired and as GOP-led conference committee members from the House and Senate continued to negotiate.

Stabenow is seeking a sixth term from Michigan voters in a state where dairy is one of the major agricultural products along with corn and soybeans. She is facing Trump-endorsed conservative Republican John James, an Iraq War veteran who has been climbing in recent polling and accused Stabenow of "willing to hurt farmers because she opposes work requirements for able-bodied adults."

Stabenow's office didn't immediately respond to a request for comment, but she previously tweeted a response to Trump's swipe that the Senate bill was passed with 86 votes, or the most ever for a farm bill.

"I'm not letting politics distract me from working across the aisle to finalize a good bill that will deliver certainty for farmers and families in Michigan and across the country," Stabenow tweeted.

The joint House-Senate conference committee working to resolve differences in the legislation has continued to hold discussions despite the election recess.

"Farm Bill negotiations are ongoing, and members and staff are meeting regularly and often to find agreement in every title," said Meghan Cline, a spokeswoman for the Senate Agriculture Committee. "The chairman and ranking members are focused on getting a new Farm Bill negotiated and passed as quickly as possible to deliver certainty to farm country."

According to House insiders, disagreements still hang out there on several issues, but one person described it as "nothing we can't work through."

The farm bill is usually renewed every five years, and the last bill expired Sept. 30. About two-thirds of the farm bill spending goes to nutrition programs such as SNAP.

The 2014 Farm Bill's expiration affected several dozen so-called orphan programs because they have authorization or funding tied to the current farm bill. Some of those programs have since received gap funding by the U.S. Department of Agriculture, including a program that provides training and other assistance to underserved and veteran farmers.

"Even with the expiration of the Farm Bill, farmers will still have the protection of the traditional farm safety net, because most commodity programs are tied to the crop year, not the federal fiscal year," USDA Secretary Sonny Perdue said in a statement. "In addition, SNAP benefits will continue to be provided to recipients."

The conference committee members are expected to meet again in early November after the election. Political analysts suggest there's still a chance of resolving differences between the two farm bill versions, but some also suggest a new bill maybe easier to reach with the new Congress, particularly if the Democrats get control of the House.

"The political problem they're facing is trying to figure out a way a bill can pass the Senate and still get a majority of the Republican caucus in the House, and it's just a really difficult equation to solve," said Ferd Hoefner, a senior strategic adviser and long-time farm bill expert at the National Sustainable Agriculture Coalition, an advocacy group for small- and mid-size farmers.

Added Hoefner, "If the Democrats are controlling the House and doing a bill next year, the House bill will come out looking exactly like what the Senate bill looks like now. The Senate will just do the exact same bill, presumably, and so it makes it easier under that circumstance to reach a negotiated settlement, because the bills will start out much easier to reach a negotiated settlement."