One of the most contentious policies of President Bush’s first term was a proposal to grant the estimated 8 million to 12 million undocumented immigrant workers in America a path to legal status. Rejecting a general amnesty, the president called his proposal a temporary-worker program. Last week he indicated he would act on his words, no doubt encouraged by Election Day polls showing that 44% of Hispanic voters chose Mr. Bush, up from 35% in 2000.

But if the president intends to use his second-term mandate to reform the country’s broken immigration system, it will be a tough road, requiring a careful approach to a growing problem that defies party lines.

“It’s not a partisan issue. Both parties are split on it,” said sociologist Nathan Glazer, a professor emeritus at Harvard University and co-author of “Beyond the Melting Pot.” “On the Democratic side, there are those who are just friends of immigrants, then there are also those who are concerned about [immigrants’] impact on wages. And the Republicans are divided between the business-oriented groups and those who are more nationalistically focused.”

Mr. Bush’s proposal attempts to appease immigrant groups and employers, by giving foreigners a legal way to work in America, as well as those concerned about unchecked immigration, by providing incentives for temporary workers to return home after their work visas are completed.

“The system is not working,” Mr. Bush said in a speech last January when he introduced the proposal. “Out of common sense and fairness, our laws should allow willing workers to enter our country and fill jobs that Americans are not filling. We must make our immigration laws more rational, and more humane. And I believe we can do so without jeopardizing the livelihoods of American citizens.”

The proposal includes two key components: a renewable temporary work visa available for immigrants to fill jobs not being taken by American citizens, and a similar visa for undocumented immigrants already working illegally in America, who must also pay a fine for breaking the law.

Despite the president’s announcement, the proposal was not linked to any specific legislation, and observers say it will probably take years for a substantial change in the law.

Indeed, the effort appeared stalled until last week, when Secretary of State Powell promised action at talks in Mexico City and Mr. Bush met with Senator McCain, a Republican of Arizona who is author of the immigration bill that is most similar to the president’s proposal.

It was a hopeful sign that reform is on the horizon, said a senior fellow at the Manhattan Institute, Tamar Jacoby.

“I think he’s determined to do it,” said Ms. Jacoby of the president’s intentions.” There are a lot of details, getting what can work and then getting the right centrist combination. Business and labor are both very interested in it, but they have very different ideas about how it should work.”

In general, she said, the majority of Democrats support immigration reform. Republicans are divided between about a third who want to clamp down on immigration, a third who support it, and a third who are still undecided.

Labor is one of the newest additions to an alliance of unlikely bedfellows that supports immigration reform, including Alan Greenspan, farmers, and a wide spectrum of immigrant groups. Their reasons for supporting reform range from the dearth of Americans willing to take bottom-rung jobs to national security issues, with millions living here under the radar of American law enforcement.

Agriculture is one sector of the economy where the need for reform is most evident.

“We need to have a recognition that a large percentage of agricultural workers have fraudulent work documents,” said the executive vice president of the National Council of Agricultural Employers, Sharon Hughes. “Fifty to 70% have fraudulent documents, and the growers have no way of knowing until someone comes around doing enforcement or they get Social Security ‘no match’ letters.”

Ms. Hughes, whose group has been lobbying for immigration reform for nearly a decade, has been pushing the AgJobs Bill, a temporary worker program for agricultural workers that is also similar to the president’s proposal. It is one of a handful of bills in Congress that attempts to address specific issues of immigration reform. Another one would provide education for undocumented students

“Now that the elections are behind us, I think we have a good chance to get something done in our sector,” Ms. Hughes said. “We’ve been at this a long time and we really need to get something done.”

The linchpin for any immigrant reform, according to many observers, will be how the immigrants already working illegally in America fit into the program, an issue the president has yet to definitively address.

In his speech, Mr. Bush said he “opposes amnesty” and the program “expects temporary workers to return permanently to their home countries,” but that some workers will choose to pursue citizenship and will be allowed to do so. Speaking from Mexico last week, Mr. Powell affirmed the president’s commitment to reform, but cautioned against keeping expectations too high for a rapid and complete overhaul.

One concern expressed by immigrant and labor groups about the president’s proposal is that it might replicate the bracero program, a guest-worker program during World War II, in which “we exploit them and everyone has to leave at the end,” said Ms. Jacoby of the Manhattan Institute.

“We don’t want to be a rich middleclass country with a poor (immigrant) working class,” said Ms. Jacoby, who is the editor of “Reinventing the Melting Pot.” “That corrodes our democratic ideal of what kind of country we are.”

In spite of Mr. Bush’s assurance that the program would not promote illegal activity, critics call it an amnesty in disguise that it is rewarding immigrants who broke American laws and are undercutting citizens for jobs.

“It’s probably the most radical immigration proposal any president has ever offered. It’s breathtaking and would destroy whole occupations,” said the director of the Center for Immigration Studies, Mark Krikorian. Still, Mr. Krikorian, who supports restricting immigration, does not believe the Republican-controlled Congress will support the proposal, saying, “Congress is not going to pass any of that.”

The chairman of the Immigration Subcommittee of the House Judiciary Committee, Rep. John Hostettler of Indiana, told the Washington Times last week that passage of Mr. Bush’s guest-worker program is unlikely in the House. “We have held hearings in the 108th Congress that indicate such a program would continue a long-term downward spiral in the wages of low-skilled and no-skill workers,” he said.

Even immigration experts, who urge the necessity of changing the country’s system, question whether Mr. Bush is up to the challenge of passing such a massive immigration reform.

“I’d be very surprised if anything but lip service and more ‘beef up the border’ were the result,” said an immigration historian, Roger Daniels. “Bush has said some good things about immigration, but he hasn’t done any of them as president. He has left his good buddy in Mexico high and dry.”