“EVERY major policy issue has been resolved,” declared Charles Schumer, one of eight senators seeking to draft a bipartisan bill to reform America’s immigration system. The “Gang of Eight”, he continued, would unveil their proposal in days; it would putter through the Judiciary Committee this month, and reach the Senate floor in May. “We’re on track,” he concluded, in a television interview this week. If he is right, an issue that has dogged American politics for a generation, left 11m people in limbo and steadily undermined the Republican Party’s prospects, is on the verge of resolution. Not everyone, even within the Gang of Eight, seems quite so confident. Marco Rubio, the group’s most conservative member, says reports of success “are premature”. At least one element of the bill, a scheme to admit agricultural workers on a temporary basis, has proved especially thorny to negotiate. Many Republicans are still averse to any reprieve for America’s 11m illegal immigrants, despite the dreadful showing this stance earned them among Hispanic voters at last year’s elections. But the momentum in favour of reform is clearly building.

Mr Schumer’s crowing was prompted by a deal on visas for low-skilled workers between the two pressure groups to which the gang had delegated the subject: the AFL-CIO, America’s biggest confederation of trade unions, and the United States Chamber of Commerce, which represents business. Bickering on this topic contributed to the collapse of the last big push for immigration reform, in 2007. This time the two sides have agreed on an elaborate formula which would hand out more visas when the economy is strong and fewer when it is weaker. Businesses would benefit from the admission of as many as 200,000 workers a year when times are good (and as few as 20,000 when they are not). The unions, meanwhile, are pleased with wording intended to prevent an influx of new labour from depressing wages or undermining workers’ rights. The main beneficiaries, naturally, would be the visa recipients, who would be allowed to change jobs and apply for permanent residence after a year—as they cannot do now.

The gang’s bill is expected to boost the number of visas for skilled workers too, especially in high-tech fields, and to make it easier for foreign graduates of American universities to settle in America. The senators are also rewriting the rules on the admission of seasonal farm labourers, a job largely filled by illegal immigrants at the moment, thanks in part to the cumbersomeness of the official scheme. They had hoped to win the approval of both growers’ associations and the United Farm Workers (UFW), the biggest agricultural union. But the two sides are at an impasse. The farmers had wanted to adjust the official formula for setting the guest workers’ wages; the union complained that they were trying to suppress wages in general.

Nonetheless, the dispute is unlikely to derail the bill, because the main concern of both sides is not regulating the future flow of new farm workers, but normalising the status of those who are already in America. The country’s 11m “undocumented” immigrants represent a huge pool of recruits for the unions and new hires for business. Although most of them work, their shadowy status exposes employers to legal penalties and the immigrants themselves to exploitation. The Gang of Eight has agreed that their bill will provide these unfortunates not only with some sort of formal legal status, but also with the chance to become citizens eventually.

Just how arduous that process is will be the main point of contention when the bill is unveiled. Republicans have long resisted anything that smacks of amnesty. Democrats, meanwhile, warn against any requirements that are so onerous as to exclude large numbers of the undocumented. The Gang of Eight has already agreed that most illegal immigrants will have to prove that they have worked, pay back taxes and pass both a background check and a test of civics and English, among other requirements, before they can become permanent residents and, eventually, citizens.

The path to citizenship can be long, argues Angela Kelley of the Centre for American Progress, a left-leaning think-tank, as long as it is wide. Many immigrants would struggle to prove their employment history, she notes, since those who hire them are breaking the law and thus tend to avoid much of a paper trail. By the same token, fees or fines that might seem lenient to a middle-class Republican primary voter would be unaffordable for many illegal immigrants. $10,000, for example, would represent over a third of annual household income for half of those in America illegally, according to the Migration Policy Institute, a pro-immigration think-tank.

Another issue bound to provoke debate in the Senate is the policing of America’s borders. The Gang of Eight has agreed that security must get tighter before any illegals can receive green cards (the document conveying permanent residence), to prevent a wave of new immigrants seeking to exploit the reforms. In fact, security on the Mexican border is already fearsome, and unauthorised crossings are at their lowest levels in decades (although the weak economy on the northern side and declining birth rates on the southern one also play a part). Moreover, it is impossible to seal such a long and rugged frontier completely. That leaves Democrats fearful that Republicans will set an unreasonable standard, and Republicans suspicious of a Democratic fudge. A possible solution, suggests Ms Kelley, is to set objective goals, in terms of miles of fencing built, numbers of border-patrol agents deployed, and so on.

Immigration advocates seem confident that these hurdles will be overcome, because the political logic in favour of a deal is so strong. They point to the many Republicans who have moderated their opposition to immigration reform since the elections. Rand Paul, a libertarian senator with a big tea-party following, recently made positive noises. Eric Cantor, the number two in the Republican hierarchy in the House of Representatives, has dropped his opposition to a scheme to give green cards to certain illegal immigrants brought to America as children. The involvement of Mr Rubio, another darling of the tea party, gives the initiative credibility on the right. It is telling that opponents of reform have taken to complaining less about the substance of the proposals and more about the haste with which they are being pursued.

The overwhelming majority of the Senate’s 53 Democrats and two independents are expected to support the reforms, leaving only a handful of Republican votes needed to reach the 60 vote threshold to overcome a filibuster. At the very least, the four Republican members of the Gang of Eight are likely to support their own bill, along with a few other moderates. The mechanics in the House are more complicated: its Republican majority includes many fierce opponents of any leniency towards illegal immigrants. But the Republican leadership, says Jeff Hauser of the AFL-CIO, will not want to be seen as sabotaging the reforms. In the end, he predicts, they will allow a vote on any bill the Senate produces, in the expectation that it will pass mainly with Democratic support. Shepherding an immigration bill through Congress may be a daunting task, but snuffing one out is beginning to look more daunting still.