There is no reason that Congress can't pass an immigration overhaul by the end of summer, U.S. President Barack Obama said.

In his weekly radio and Internet address, Obama pushes a bipartisan bill the Senate is debating that creates a pathway to citizenship for 11 million people in the U.S. illegally.

Obama says the bill's opponents will do everything possible to stop it. He says they'll play politics, stoke fear and divide people.

He says if they succeed, the nation will miss a chance to fix a badly broken system. He's urging Americans to tell their lawmakers we must get immigration done.

In the Republican address, Rep. Luke Messer of Indiana says House Republicans have acted to prevent a student loan rate increase next month. He says Senate Democrats should stop stalling.

Passing an immigration bill may seem simple, given that the White House, organized labor and the Chamber of Commerce all support the measure; and that many Republican political strategists want the GOP to show a more welcoming face to Hispanic voters.

But it won't be.

Presidential ambitions alone will see to that, as Sen. Marco Rubio, for one, attempts a political straddle while other potential GOP presidential candidates firmly oppose the measure.

The Florida Republican helped negotiate the bipartisan bill now headed to the full Senate, and recently has called for changes as he tries to keep faith with tea party supporters and other conservatives who will vote in the 2016 primaries and caucuses.

Internal divisions in the Republican party, deeply held differences over policy, concerns over costs and more add to the complexity of legislation that Senate Majority Leader Harry Reid, D-Nev., has said must come to a final vote by July 4.

"In truth, the bill is amnesty first and a promise of enforcement later," Sen. Jeff Sessions, R-Ala., said Friday, previewing points he and other conservative opponents intend to make over the next three weeks.

The bill's requirement for payment of back taxes "is toothless," the promised steps to secure the border "will not work" and millions of immigrants currently in the country illegally would qualify for welfare in five years, Sessions said. The measure "actually weakens current law in quite a number of significant areas" when it comes to immigration cases tried in the courts, he added.

Sessions derided the bipartisan coalition behind the measure as a collection of outside groups that do not represent the national interest.

In a reflection of the GOP divide, he took issue with Karl Rove, the former top strategist for President George W. Bush, whose own attempt at immigration overhaul flamed out in 2007.

Writing in the Wall Street Journal recently, Rove warned Republicans to be mindful of solid public support both for secure borders and for a path to citizenship for those in the country illegally.

He urged GOP lawmakers to avoid use of the term "amnesty," which he said is "forgiveness of wrongdoing without penalty."

The legislation imposes financial costs on immigrants now in the country illegally who seek citizenship.

At its controversial core, the legislation creates a 13-year route to citizenship for an estimated 11.5 million immigrants currently in the United States illegally. It also sets border security goals that the government must meet before any change in legal status is granted to immigrants.

As drafted, the legislation also creates a low-skilled guest-worker program, expands the number of visas available for high-tech workers and de-emphasizes family ties in the system for legal immigration that has been in place for decades.

In the background are questions about the economic impact of the legislation at a time federal deficits are high and the economy is mounting a slow recovery from recession.

The Congressional Budget Office has yet to estimate the legislation's impact on the deficit, although supporters acknowledge that changes will be necessary if the agency ultimately predicts the measure would result in additional red ink.

Sessions and others say it will.

"Since an overwhelming number of the workers here today are lower-skilled that are illegal ... you can expect their incomes to be low, they'll qualify for the earned income tax credit, for Medicaid, and program after program, food stamps and others," Sessions said Friday.

He cited a study by the conservative Heritage Foundation estimating that government costs for individuals whose residency status will be made legal will add $6.3 trillion to the deficit over 50 years.

Sessions didn't say so, but the study has been widely criticized from the left and right. It was partially authored by an economist whose 2009 dissertation claimed immigrants have lower IQs than the "white native population" in the United States.

Also looming as the debate moves onto a more national stage are scarcely submerged racial tensions.

Both Sessions and Sen. Mike Lee, R-Utah, referred to them Friday. Some on the other side of the issue touched on race when the Republican-controlled House voted Thursday to resume deportation of immigrants brought to the United States illegally as children, many of them from Mexico or other Central or South American countries.

Supporters of the legislation sometimes claim that its opponents are "somehow anti-immigrant, or you're an uncompassionate person, that your heart is made of stone, that your ribs are made of concrete and that you have no heart," said Lee. He called such comments "beneath the dignity" of the Senate.

Said Sessions: "There's a lot of power behind this legislation. I can feel it. When I raise questions, push-back comes. 'You're unkind. You don't like immigrants,'" he said, paraphrasing the criticism.

"That's offensive to me."

Supporters of the general approach taken by the legislation make it clear the criticism isn't going to stop.

"House GOP gives the proverbial middle finger to the Latino community with vote" to deport younger immigrants, former Obama aide David Plouffe tweeted shortly after the House acted.

Based on reporting by The Associated Press.

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