As the Senate worked on landmark immigration reform, leading up to a bipartisan bill it passed Thursday, Republicans in the U.S. House of Representatives repeatedly said they would never rubber-stamp the other chamber’s measure.

Now, the moment has come — immigration reform is now about to hit the House floor, the real battlefield for this effort, observers said.

Unlike the Senate, where Democrats hold a majority, the House is under Republican control, and a conservative faction is vocal and steadfast in its refusal to approve what it calls an amnesty, a reward for law breakers.

It’s still a bit of an enigma what will actually happen in the House — immigration reform legislation could emerge stronger, or bruised and weakened, or perhaps even just die there.

House Republicans plan to hold a special closed-door meeting July 10 on how to proceed with immigration.

At stake in the House, experts said, is much more than the vexing matter of what to do about an undocumented population that the most estimates put at 11 million — larger than the population of some states, such as New Jersey and Georgia.

At stake is nothing short of the future of Rep. John Boehner’s role as House Speaker and even his legacy, as well as the individual careers of Republican House members, analysts said.

Some went even further, arguing the future of the party itself is in question.

“House members are generally more hued to the likes and dislikes of their constituencies back home -- than thinking more broadly about the country -- than their brethren in the Senate,” said Demetrios G. Papademetriou, president of the Migration Policy Institute, a Washington-based think tank.

They’re more ideological, too. 

Although many saw the hard line immigration views of some prominent Republicans last year as a key factor in the loss of GOP candidate Mitt Romney to Barack Obama in the presidential race, and said the party could not continue to alienate Latinos if it wanted a political future, others questioned whether it will matter in the House’s handling of immigration reform.

“Calculations show that there are about 146 Republican districts where Latino voters are less than 10 percent,” said Tamar Jacoby, president of ImmigrationWorks USA, an umbrella association of employers pushing for improving the immigration system.

“They vote on their re-election,” Jacoby continued. “In the 1950s, party leaders could say to Congress ‘Here’s my agenda, I need you to vote for it, I’ll protect you, I’ll give you an appointment on a committee, I’ll give you what you need to build that bridge in your district.'”

But it doesn’t work that way today, she said.

“The way people in Congress vote has to do with back home, with what’s in their heads,” she said.

A bipartisan Senate group, called the “Gang of Eight,” spearheaded immigration reform to include tightened border security, a pathway to legal status for many of the nation’s undocumented immigrants, expanded guest worker visas and stricter rules for employers regarding hiring people authorized to work in the United States.

Whether the hawks, such as Rep. Steve King, the Iowa Republican who is firmly against a pathway to legalization, tilt the immigration discussion in the House, or soften their stance to go along with more moderate colleagues, remains to be seen.

“When they go home for the [July 4th] holiday, they will have town hall meetings and talk to their constituents about immigration,” said King of his colleagues in the House. “We will have long discussions about immigration. And what they hear will be reflected in the July 10 meeting.”

If Congress is different now than how it was in the 1950s, so is the American public, which polls show tend to be more open to reforming immigration in a way that was unthinkable even in 2007, when the last major attempt to overhaul the system took place — and failed.

Not only has the country’s demographics changed — putting more Latinos and Asians, for instance, in voting booths — but young undocumented immigrants who have grown up in the United States have moved to the forefront of the push for a path to legal status.

They have held rallies, press conferences and taken to social media to put a human face on illegal immigration, and appeal to Americans to see them as Americans, too.

“Once you take a class of people and you promise them things, you energize them, and they get people to listen,” it’s impossible to reverse the momentum, Papademetriou said.

“Three years ago, you didn’t have that narrative, about immigrants who grew up here, who can contribute, who had nothing to do with their parents’ decision to come here illegally,” said Papademetriou, of the Migration Policy Institute.

“Now there’s been an extraordinary reversal. Now it’s the skeptics about immigration and immigration reform who are having a hard time being heard,” he added.

Many experts believe there will be immigration reform, perhaps this year or early next year — but what shape it will take, and how it will address a pathway to legalization, is anyone’s guess.

“There are three things the House has to decide,” said Audrey Singer, an immigration expert at the Brookings Institute, a think tank in Washington, D.C. “The content of the bill, the timing of the process, and whether it will be one bill or several bills.”

House GOP leaders have often stressed that they disagree with approaching a solution to immigration in one massive measure. They prefer, they have said, a piecemeal approach — considering smaller, separate bills that deal with a particular aspect of immigration.

Both parties, experts said, are feeling pressure to fix the immigration system, which people on all sides of the issue agree is deeply flawed. And Obama, they said, also is under pressure to come through on his 2008 campaign promise to reform the system.

Boehner said this week that he will not go against his party in handling immigration.

"The House is not going to take up and vote on whatever the Senate passes,” he told reporters. “We're going to do our own bill through regular order, and it'll be legislation that reflects the will of our majority and the will of the American people.

His constituency comes first, Boehner said.

“And for any legislation, including a (final bill), to pass the House, it's going to have to be a bill that has the support of the majority of our members,” said the Ohio Republican.

A story in The Hill newspaper noted that “Boehner has faced criticism in his own party for passing major legislation — including the bill at the start of the year to avert the ‘fiscal cliff’ by relying on the support of House Democrats to overcome the opposition of conservative Republicans.”

This time, Boehner vowed, he would not repeat that tactic.

King, of Iowa, said the so-called rule-of-law-conservatives, those who generally oppose a pathway to legal status in immigration reform, have grown to about two in the House earlier this year to between dozens and scores now.

Some long-time immigration policy observers are doubtful that any reform bill will pass in the current climate, with bipartisan bickering and the tensions between Republicans and Obama.

“You see warnings from House Republicans that Boehner will lose his job if he goes along” with a measure the party’s conservative base opposes, said Mark Krikorian, who heads the Center for Immigration Studies, a think tank which favors a strict approach to immigration policy.

“The Senate bill is dead on arrival,” Krikorian said. “Until there’s a Republican president who is hawkish on immigration, and who demonstrates his commitment to enforcement, you won’t see any broad movement to legalize anybody.”

Krikorian said many Republicans simply do not — and will not —trust Obama with immigration reform.

“The result might be that Obama extends deferred action, like he did with the DREAMers, to their parents,” said Krikorian. “He could take it further, which will just infuriate House Republicans even more.”

Elizabeth Llorente can be reached elizabeth.llorente@foxnewslatino.com

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