Thwarted in their past efforts to address a critical labor shortage, the agricultural lobby and farm workers are pressing their Congressional allies to bring up a controversial guest-worker program as the Senate kicks off farm bill discussions this week.

But in doing so, they concede they risk injecting the poison pill of immigration into the popular agriculture bill, which reauthorizes federal programs affecting farms in virtually every state.

And within the immigration issue lies an even more emotionally laden subset: “Some will try to tag it as amnesty,” notes Craig Regelbrugge, the co-chairman of the Agriculture Coalition for Immigration Reform, which boasts 300 national, regional and state groups that produce everything from vegetables to poultry to Christmas trees.

Indeed, Sen. Jeff Sessions (R-Ala.), who successfully led efforts to shut down comprehensive immigration reform in July, earlier this month said he would mount opposition to attach immigration-related amendments to must-pass legislation such as the farm bill or Defense authorization bill.

“We may be headed into another immigration battle,” Sessions said, adding that such efforts likely would “blow up on the floor” of the Senate.

Majority Leader Harry Reid (D-Nev.) last week pulled another immigration-related amendment from the Defense bill after Republicans objected. The bill, known as the DREAM Act, allowed a pathway to legal status for undocumented immigrants who came to the United States at a young age if they attend college or join the military. Reid vowed to bring it up again at a later date.

Nonetheless, the United Farm Workers — the farm workers’ union founded by Cesar Chavez — is bringing dozens of its members to Washington this week to press Congress to support the Agricultural Job Opportunities, Benefits and Security Act, or AgJOBS.

The bill (S. 340), sponsored by Sen. Dianne Feinstein (D-Calif.) and a bipartisan group of 30 Senators, establishes a process for undocumented agriculture workers to obtain temporary legal status, along with the possibility of permanent green-card status down the road. It also could be offered as an amendment to the larger farm bill.

The House already passed its version of the massive five-year reauthorization bill in July without such provisions for seasonal agriculture workers.

The proposed Senate legislation is intended to address a shortage of workers to harvest crops, which the bill’s supporters say results in billions of dollars in crop losses each year. The situation has been exacerbated by immigration crackdowns.

At least 70 percent of U.S. farm workers lack proper work authorization and immigration status, Regelbrugge says.

The visit by the union, which along with the farm lobby played a key role in helping shape the bill, comes as the Senate Agriculture, Nutrition and Forestry Committee is poised to take up the Senate farm bill, possibly as early as this week.

Feinstein spokesman Scott Gerber on Friday confirmed that the farm bill is one option the Senator is considering. “We’re continuing to work and build support for it,” he said. Reid also has backed tying the measure to the farm bill.

Regelbrugge said the farm bill may be the next best option for passing the measure, after the collapse of comprehensive immigration reform earlier this year. “[AgJOBS] enjoys the symbolism of being tied to agriculture and enjoys broad bipartisan support,” he said. Other legislative vehicles, like appropriations bills, would be more problematic, he added.

But proponents must first overcome the “amnesty” label Sessions has given the bill. In an August letter to their colleagues, Feinstein and Sen. Larry Craig (R-Idaho), who also was instrumental in helping draft the bill, dismissed the amnesty label as “simplistic and inaccurate.”

“U.S. agriculture will not be helped by name-calling and histrionics, but by support for the thoughtful, desperately needed reforms contained in AgJOBS,” the pair wrote.

Sessions’ office did not respond to a request for comment.

As the chief GOP proponent of the measure, Craig’s legal troubles also complicate efforts to fend off Republican criticism.

Craig spokesman Dan Whiting said Friday that while the farm bill is a natural fit for AgJOBS, the Senator currently is not pressing the issue.

Regelbrugge concedes that AgJOBS could lead to citizenship for participants, but he notes that such candidates would still have to comply with separate federal requirements to qualify, including a five-year waiting period. “AgJOBS does not preclude eventual citizenship but is hardly an ‘automatic path’ as some will allege,” he said.

The issue also divides Sens. Tom Harkin (D-Iowa) and Saxby Chambliss (R-Ga.), the chairman and ranking member, respectively, on the Agriculture Committee.

Harkin spokeswoman Kate Cyrul last week noted that Harkin is a co-sponsor of AgJOBS but said it would be “very challenging” to add it to the bill because of the immigration debate.

For his part, Chambliss is strongly opposed to AgJOBS, said spokeswoman Lindsay Mabry. “Immigration issues should be dealt with separately,” she said.