“It's opening day” for an overhaul of immigration policy, said Frank Sharry, a leader of the coalition that unites Hispanic rights groups, labor unions and church organizations with an array of business interests clamoring for wider access to low-wage workers.

The volatile politics of immigration policy took a turn in November's midterm election as Democrats, historically aligned with groups who seek to expand immigration, took control of both houses of Congress.

Many Democratic candidates won after taunting the “do-nothing Republican Congress” for its failure to manage immigration and its passage of legislation to build a border fence without funding it.

“That became a laugh line to show how ridiculous Republicans were,” said Sharry, executive director of the National Immigration Forum.

The leader of a Washington think tank that argues for restrictions on immigration said that if House Speaker Nancy Pelosi, D-San Francisco, wants to preserve the Democratic majority, she will need to move cautiously on immigration. While a sweeping legalization measure would appeal to much of the party's base, it could endanger the seats of newly elected Democrats, said Mark Krikorian, executive director of the Center for Immigration Studies.

Krikorian prefers to call legalization “amnesty,” a term shunned by immigrant advocates who speak of “earned adjustment.”

“A big amnesty would be a big problem for the Democrats who won in swing districts,” Krikorian said. “In the next election, challengers would be able to run against the 'left-wing Nancy Pelosi amnesty.' ”

Many of those swing districts are in areas of the country where there is widespread alarm at the nation's rapid growth of illegal immigrants – estimated at 12 million and increasing at 500,000 a year.

Illinois Rep. Rahm Emanuel, chairman of the House Democratic Caucus, has said he expects the Bush administration to persuade at least 85 Republicans to vote for the legalization measure.

“They're going after Republicans because they know they're going to have to give some of their own members a bye when this comes up for a vote,” said Rep. Tom Tancredo, R-Colo., who is weighing a 2008 presidential bid to showcase his hard-line stance against illegal immigration.

Tancredo said the Bush administration is trumpeting its ramped-up enforcement measures at the border and at job sites to win the votes of reluctant members.

“They want to tell Congress, 'We've done our job, now you do yours with a guest-worker program,' ” Tancredo said. “My message is that as soon as you give them a guest-worker program, that will be the end of enforcement.”

Partisans are waiting for President Bush to state his position on one of the most controversial issues before Congress: Should workers who come to the United States on future guest-worker visas be put on a path to citizenship or required to return home?

“He has been deliberately ambiguous on that one,” said Sharry, pointing to Bush's previous calls for Congress to “match willing workers with willing employers” without stating the terms of such an arrangement.

White House spokesman Scott Stanzel this week said that such a program “must be truly temporary, so participation should be for a limited period of time and guest workers would have to return home” after a period set by Congress.

Tamar Jacoby, an immigration advocate and scholar at the free-market, pro-business Manhattan Institute think tank, said Congress must move on immigration legislation before the fall, when the 2008 presidential campaign will make both parties reluctant to act on such a controversial issue.

“I would say that it's a universal belief that if it doesn't happen by August, we're cooked,” Jacoby said.

If a wide-ranging measure fails, immigrant advocates might then look to less ambitious reforms, such as the Agjobs bill that would provide a path to citizenship for hundreds of thousands of farmworkers and their families, or the Dream Act, to provide a path to citizenship for people who came illegally to the United States at an early age, many of them brought by their parents.