WASHINGTON - Side by side, leading Democratic and Republican senators pledged Monday to propel far-reaching immigration legislation through the Senate by summer providing a possible path to citizenship for an estimated 11 million people now in the U.S. illegally.

The senators acknowledged pitfalls that have doomed such efforts in the past, but they suggested that November's elections - with Hispanics voting heavily for President Barack Obama and other Democrats - could make this time different.

Passage of the emotionally charged legislation by the Democratic-controlled Senate is far from assured, and a taller hurdle could come later in the House, which is dominated by conservative Republicans who've shown little interest in immigration overhaul. Obama will lay out his own proposals Tuesday, most of which mirror the Senate plans.

Besides the citizenship provision, including new qualifications, the Senate measure would increase border security, allow more temporary workers to stay and crack down on employers who would hire illegal immigrants. The plans are still short on detail, and all the senators conceded that months of tedious and politically treacherous negotiations lie ahead.

But with a re-elected Obama pledging his commitment, the lawmakers argued that six years after the last sustained congressional effort at an immigration overhaul came up short in the Senate, chances for approval this year are much better.

"Other bipartisan groups of senators have stood in the same spot before, trumpeting similar proposals," said Sen. Charles Schumer, D-N.Y. "But we believe this will be the year Congress finally gets it done. The politics on this issue have been turned upside down," Schumer said, arguing that polls show more support than ever for immigration changes and political risk in opposing it.

"Elections. Elections," said Sen. John McCain, R-Ariz. "The Republican Party is losing the support of our Hispanic citizens. And we realize that there are many issues on which we think we are in agreement with our Hispanic citizens, but this is a pre-eminent issue with those citizens."

Obama got 71 percent of the Latino vote in November compared to 27 percent for Republican Mitt Romney.

The president will endorse the Senate process during an event in Las Vegas Tuesday, administration officials said. He will outline a similar vision for overhauling the nation's immigration laws, drawing on the immigration "blueprint" he first released in 2011.

The blueprint focuses on four key areas: a pathway to citizenship for the 11 million illegal immigrants in the U.S., improved border security, an overhaul of the legal immigration system and making it easier for businesses to verify the legal status of workers.

Seeking to ramp up pressure on lawmakers, the White House has prepared formal immigration legislation that it could sent to Capitol Hill should the Senate process stall, administration officials said. The officials spoke on the condition of anonymity in order to discuss internal strategy.

Like the president's blueprint, the Senate proposals also call for a path to citizenship for illegal immigrants already here. But lawmakers want the creation of that pathway to be contingent upon securing the border and better tracking of people in the U.S. on visas.

The Senate's five-page framework also calls for overhauling the legal immigration system, including awarding green cards to immigrants who obtain certain advanced degrees from American universities, creating an effective high-tech employment verification system to ensure that employers do not hire illegal immigrants in the future and allowing more low-skill and agricultural workers.

In a sign of the challenges ahead, the proposals immediately got a cool reaction from Senate Republican Leader Mitch McConnell of Kentucky.

"This effort is too important to be written in a back room and sent to the floor with a take-it-or-leave it approach," McConnell said. "It needs to be done on a bipartisan basis and include ideas from both sides of the aisle."

Sen. Jeff Sessions, R-Ala., said on the Senate floor, "No one should expect members of the Senate are just going to rubber-stamp what a group has met and decided."

Sen. Ted Cruz, R-Texas, said he was concerned about the proposed path to citizenship.

"To allow those who came here illegally to be placed on such a path is both inconsistent with rule of law and profoundly unfair to the millions of legal immigrants who waited years, if not decades, to come to America legally," said Cruz.

A year after Border Patrol apprehensions of illegal border crossers plunged to the lowest levels in nearly 40 years agents have seen a slight increase in arrests, according to Border Patrol arrest data obtained by The Associated Press. In the budget year that ended in September, Border Patrol agents arrested 356,873 would-be border crossers along the Mexican border. In fiscal year 2011, agents along the Mexican border made 327,577 arrests.

Senate Majority Leader Harry Reid, D-Nev., applauded the framework and said, "I will do everything in my power to get a bill across the finish line."

Pressures from outside groups from business to organized labor to immigrants themselves will be immense, even as lawmakers warily eye voters for their reaction.

Besides McCain and Schumer, the senators endorsing the new principles Monday were Democrats Dick Durbin of Illinois, Robert Menendez of New Jersey and Michael Bennet of Colorado and Republicans Lindsey Graham of South Carolina, Marco Rubio of Florida and Jeff Flake of Arizona.

Several of them have worked for years on the issue. McCain collaborated with the late Democratic Sen. Edward M. Kennedy on the comprehensive immigration legislation pushed by then-President George W. Bush that failed in 2007.

The group claims a notable newcomer in Rubio, a potential 2016 presidential candidate whose conservative bona fides may help smooth the way for support among conservatives wary of anything that smacks of amnesty. Rubio has been working with the group while also detailing his own similar immigration proposals to selected media, getting a generally positive reaction from conservative media.

"There are 11 million human beings in this country today that are undocumented. That's not something that anyone is happy about; that's not something that anyone wanted to see happen, but that is what happened. And we have an obligation and the need to address the reality of the situation that we face," Rubio said Monday.

As the group turns to the work of writing legislation, which they hope to see come to a vote in the Senate Judiciary Committee in March, there may be most disagreement over the path to staying in the U.S. legally. In order to satisfy the concerns of Rubio and other Republicans, the senators are calling for the completion of steps on border security and oversight of those here on visas before taking major steps forward on the path to citizenship.

Even then, those here illegally would have to pass background checks and pay fines and taxes in order to qualify for a "probationary legal status" that would allow them to live and work here - and not qualify for federal benefits - before being able to apply for permanent residency, a critical step toward citizenship. Once they are allowed to apply they would do so behind everyone else already in line for a green card within the current immigration system.

That could be a highly cumbersome process, but how to make it more workable is being left to future negotiations. The senators envision a more streamlined process toward citizenship for immigrants brought here as children, and for agricultural workers.

Outside groups including Latino advocacy organizations, the U.S. Chamber of Commerce and organized labor were quick to praise the emerging framework. But some also sounded notes of caution.

Richard Trumka, president of the AFL-CIO, questioned a proposal by the Senate group to require illegal immigrants to provide proof of employment before they can gain legal status. Trumka said it could exclude millions of workers "who cannot prove employment because they have been forced to work off the clock or have no employer by virtue of being independent contractors."

Deepak Bhargava, executive director of the Center for Community Change, questioned the process being set out for the path to citizenship. "If the details are not done correctly, the path to citizenship can take far longer than it is reasonable. There is real concern about those details," he said.

Associated Press writers Julie Pace and Luis Alonso Lugo contributed to this report.