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.

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.”

Path to citizenship

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.

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.

The Department of Homeland Security also announced it will no longer scoop up undocumented immigrants arrested for minor offenses such as traffic tickets, and that it is phasing out a controversial but popular program, known as 287(g), which granted police and sheriff’s deputies the power to start the deportation process on arrested illegal immigrants.

Policy, not politics

The highest hurdle to any agreement will likely be in the House of Representatives. The Republican-controlled House has long been resistant to a comprehensive plan. Leaders on this issue, such as Rep. Raul Labrador of Idaho, a tea party-backed member and Puerto Rico native, have instead called for a more piecemeal approach.

Labrador on Monday questioned whether the Democrats wanted a political victory or a policy victory. Democrats can’t just “draw a line in the sand” and refuse to compromise and then blame Republicans if it fails, he said in an interview.

State reconsiders changes

When Republicans in North Carolina put together a special committee on immigration, the expectation was they’d recommend state legislation along the lines of Arizona and Alabama.

But the special House panel disbanded abruptly last month without offering any recommendations other than calling for the federal government to do more. Lesley Clark of the McClatchy Washington Bureau contributed.