FORT WORTH, Texas -- President Barack Obama will unveil his sweeping plan on immigration Tuesday in the midst of a rapidly shifting political environment. It’s his most ambitious move yet on the emotionally divisive issue after making a series of smaller steps over the past year.

Obama first came into office on the heels of Washington’s failure to overhaul the nation’s immigration laws. Those failures in 2006 and 2007 led many cities and states to adopt their own regulations to drive out illegal immigrants.

But exit polls find that views are changing, and a growing Latino electorate has emerged as a powerful force.

The political landscape has shifted so much that even before this latest proposal, the White House has been able to quietly unveil several policy changes that undercut communities’ ability to enforce federal immigration laws and that allow more illegal immigrants to remain in the country. Meanwhile, states are taking steps to welcome illegal immigrants by, among other things, allowing them to drive.

“The tide is turning,” said Frank Sharry, the executive director of America’s Voice, which advocates for comprehensive immigration legislation. “People sort of picked up on little pieces of it, but they’re not sure whether they believe it.”

Lawmakers on both sides of the aisle have taken notice. And both Democrats and Republicans see the debate as critical to their political futures: Obama sees immigration as a signature issue that he feels could help him define his legacy; Republicans see immigration as a way to appeal to Latinos and help pull the party out of the political wilderness.

On Monday, a bipartisan group of U.S. senators got ahead of the president’s announcement by presenting its own immigration plan, though it is similar to past proposals that have failed. The key elements include greater border security, a guest-worker program and beefed-up employer verification, and a path to citizenship for the estimated 11 million illegal immigrants already in the country. The plan is expected to closely align with one the president will unveil Tuesday on a special trip to Las Vegas. The White House called the Senate proposal a “big deal” because it embraces a path to citizenship.

“This is an important development,” Press Secretary Jay Carney said. “This is in keeping with the principles the president has been espousing for a long time, in keeping with bipartisan efforts in the past, and with the effort this president believes has to end in a law that he can sign.”

Regardless of the warm talk from some politicians about reaching an agreement, Obama’s and the Senate group’s bipartisan call for a path to citizenship will reignite an emotional debate over the rule of law and “amnesty,” a politically charged word with negative connotations among conservatives.

“We would be in a much better position to achieve immigration reform if the Obama administration had spent that last four years enforcing federal law rather than dismantling it,” Sen. Jeff Sessions, R-Ala., said Monday.

But quietly, a series of administration policy changes in recent months already has begun to transform how illegal immigrants live, work and go to school in the United States.

In addition to last summer’s announcement to defer deportations and give work permits to hundreds of thousands of undocumented youth, the White House announced last month that it was going to make legal permanent residency easier for many illegal immigrants who are immediate relatives of American citizens.