The new effort to reform immigration is mired in a pitched battle – but between unlikely foes.

In 2007, the public fight over immigration reform largely was between Republicans and Democrats. The bill died.

Now, the match is between conservative Republicans, and conservative Republicans.

In the middle is a new bi-partisan Senate bill that would make sweeping changes to immigration, including tightening enforcement and giving millions of undocumented immigrants a chance to live and work legally in the United States.

Conservatives and more moderate Republicans who support the bill have been diligently selling it – on Sunday news shows, in press releases, interviews with conservative talk radio hosts and meetings with fellow lawmakers. On the other side are other conservatives like U.S Senator Jeff Sessions of Alabama who seem motivated by a fear of alienating the Republican Party’s base.

Sen. Marco Rubio, Florida Republican, has launched a near-daily email blitz about the almost 900-page immigration bill, its pros and the misconceptions about it. Rubio, a Tea Party conservative, has become the spokesman, for all intents and purposes, for the bill, which he helped draft.

Last week, when conservatives in Congress tried to link the Boston Marathon bombing, in which the suspects are Chechen brothers who received political asylum, to immigration reform, Rubio quickly fired back that tying the two issues was irresponsible.

Last week, Florida Tea Party members staged a protest against Rubio, often referred to as a Tea Party darling, and who won his seat with the strong support of conservative voters and leaders.

The protesters took issue with Rubio’s backing of, and central role in, the bipartisan immigration reform bill.

Protesters with The Martin 9/12 Committee, a Tea Party group, held signs that read: “No Amnesty for Undocumented and Illegal” and “Stop the Senate!”

Jim McGovern, a founder of The Martin 9/12 Committee, and an organizer of the rally, said the protesters singled out Rubio because they feel betrayed, in a way, by their icon.

“He put himself up as a spokesperson on this [immigration] issue,” McGovern said, “at great political risk because he knew he was going to get opposition from people he considers his base.”

“We are constituents of his,” he said. “We were concerned he wasn’t listening to the real concerns of the people who elected him.”

Rep. Paul Ryan, a Wisconsin conservative and the GOP vice presidential candidate last year, appeared with Rep. Luis Gutierrez, an Illinois Democrat, this week at a rally in Chicago in a show of bipartisan support for comprehensive immigration reform. Ryan called the reform bill a job creator that everyone, especially conservatives, should get behind.

Conservatives who oppose the reform bill see the fight over it as one that actually is over something larger – the fight for the base, which has come increasingly under attack after it was blamed for having had a major role in Republican presidential nominee Mitt Romney’s bruising defeat in the November election.

Many political experts, and many Republican Party leaders, said the hardline rhetoric by Romney and others in the party on the issue of immigration alienated Hispanic voters, 71 percent of whom chose President Obama.

“This is about what direction the party is going to go in,” said Allert Brown-Gort, the associate director of the Institute for Latino Studies at Notre Dame University. “In some ways it’s really about the future role of the Tea Party within the Tea Party. It’s about those people in leadership position in the Republican Party who say we need to move past the immigration issue so that we can attract Latinos, and who say that maybe depending on just the base isn’t enough.”

In South Carolina, U.S. Sen. Lindsey Graham is up for re-election in 2014, something that conservatives who see the Republican as a turncoat because of his membership in the so-called “Gang of Eight,” consider a way to make him vulnerable.

Last week, conservatives in neighboring Georgia put up a billboard in their state taking aim at Graham, saying that he wants undocumented immigrants to move to South Carolina.

“South Carolina Welcomes the Undocumented,” the billboard read. “Sen. Lindsey Graham says His State has a Labor Shortage and Wants More Immigrants.”

The billboard, the work of a group headed by D.A. King, who helped draft Georgia’s anti-illegal immigration law, included Graham’s office telephone number and a hyperlink to an article that quoted the South Carolina senator saying that the reform bill would “save our nation from. . .a shortage of labor and a catastrophic broken system.”

It also took aim at Rubio, saying: “Help us stop the RubioObamaAmnesty.”

The more conservative part of the base, Brown-Gort said, feels disaffected, having watched the rhetoric of establishment Republicans go from embracing the most conservative positions on things such as immigration, to distancing itself from them.

McGovern agrees.

“I know there’s a sympathetic groundswell for people who would be affected directly by this immigration proposal,” he said, referring to undocumented immigrants who would be able to obtain temporary legal status, then permanent status about 10 years later. “But those of us affected indirectly watching what’s going on believe there’s a vocal minority being pandered to – to the detriment of the population at large.”

That’s where U.S. Sen. Ted Cruz, a Tea Party favorite from Texas, comes in, experts say.

Cruz, who like Rubio is Republican, conservative and Cuban-American, has been one of the most persistent and vocal critics of policies and proposals that Democrats as well as fellow Republicans are supporting.

On Tuesday, Cruz, who had said he opposes a path to legalization for undocumented immigrants, issued a press release criticizing the “Gang of Eight’s” immigration bill for, among other things, lacking specific means for assessing border security.

On Wednesday, another conservative group, NumbersUSA, whose head is Roy Beck, vowed to continue its mission to torpedo the bill.

Many on different sides of the immigration debate are watching the moves by NumbersUSA, seen as having been a major player in the defeat of the 2007 immigration reform bill, despite efforts by President George Bush to push hard for it.

Like other conservative groups, NumbersUSA is waging its fight against the bill by singling out conservative Republicans who support it.

Earlier this year, NumbersUSA released a radio ad blasting Graham for being part of a plan it said amounted to “amnesty and welfare for millions of illegal aliens.”

The ad ran in Graham’s own South Carolina, and asked: “Who elected Lindsey Graham to demand millions more immigrant workers when so many South Carolinans are jobless?”

Graham will be up for re-election soon. Rubio is seen as a possible 2016 presidential candidate.

"He apparently has made the calculation that the conservative base may be too confining," said Brown-Gort. "He has always been pragmatic. He went hard-right to win the senate election in Florida. Now he and the party are looking at the country's changing demographics."

The rift between conservatives is even spilling outside politics.

“Conservatives are bringing out allies, special interest groups,” to join this fight, Brown-Gort said.

In an incident that left even liberals agape, conservative Grover Norquist, founder and president of Americans for Tax Reform, argued in the Senate Judiciary Committee hearing on Tuesday that more immigration would boost the economy and keep the United States globally competitive.

Norquist challenged statements by Steven Camarota, of the conservative Center for Immigration Studies, who testified that undocumented and legal immigrants are a drain because they rely on public assistance and have lower education levels.

Norquist retorted that undocumented immigrants are prohibited by law from receiving public assistance, and that the Gang of Eight’s bill would not allow them to qualify.

“Gun control is one thing,” Brown-Gort said, “but for Republicans, with immigration the payoff is bringing people together, and attracting a new class of people – Hispanics, and Asians, but more so Hispanics, because there are so many more of them.”

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

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