A bipartisan group of senators outlined a far-reaching proposal Monday to overhaul the nation’s immigration laws, saying that the time has come to fix “our broken immigration system.”

At a joint news conference, five of the eight senators who signed on to a detailed statement of principles to guide the effort portrayed it as a way to resolve the plight of millions of undocumented immigrants living illegally in society’s shadows and to modernize and streamline the legal immigration system.

“We have a long way to go, but this bipartisan blueprint is a major breakthrough,” said Sen. Charles E. Schumer (D-N.Y.). He expressed hope that the Senate could pass a bill by late spring or summer.

Sen. John McCain (R-Ariz.) vowed that the overhaul would not repeat “the mistakes of 1986,” when, he said, an amnesty program legalized millions of illegal immigrants but created conditions for the illegal entry of many millions more.

The other members of the group behind the proposal are Democrats Richard J. Durbin (Ill.), Robert Menendez (N.J.) and Michael F. Bennet (Colo.), and Republicans Lindsey O. Graham (S.C.), Marco Rubio (Fla.) and Jeff Flake (Ariz.).

Immigrants living in and leaving the United States

The White House embraced the immigration proposal Monday but stopped short of pledging President Obama’s signature, noting that legislation on the issue has yet to be drafted.

“It’s a set of principles that mirror the president’s principles,” White House press secretary Jay Carney told reporters at Monday’s briefing. The president is expected to present his own proposal at an event in Las Vegas on Tuesday.

The senators’ announcement comes as a bipartisan group of House members is also working on an immigration proposal. House Speaker John A. Boehner (R-Ohio) said last week that they “basically have an agreement.”

The Senate group presented its proposal at a packed Capitol Hill news conference attended by dozens of English and foreign-language media outlets.

The group outlined the key balance in its proposed framework: Legalization would be afforded almost immediately to the nation’s 11 million undocumented immigrants, provided they pay back taxes and a fine. But the opportunity to pursue full citizenship would not become available until the border was secured and new systems were in place for employers to verify workers’ immigration status and for the government to ensure that legal immigrants cannot overstay their visas.

The document also calls for tying flows of legal immigration to the nation’s unemployment rate but generally expanding visa programs to discourage people from crossing the border without permission.

“It’s a pretty straightforward principle,” said Rubio, who switched between English and Spanish during the lengthy rollout. “It’s a principle that says we have to modernize our legal immigration system, we have to have a real enforcement mechanism to ensure we’re never here again in the future, and we have to deal with the people that are here now in a way that’s responsible but humane.”

Obstacles on Capitol Hill

Despite being authored by lawmakers of both parties, the proposal could face sharp opposition on Capitol Hill, where the last attempt at an immigration overhaul sank in 2007. Three years later, in the 2010 lame-duck session, legislation that would have provided a path to citizenship for young people who were brought to the country illegally as children fell short of passage in the Senate.

Response from the GOP on Monday was mixed. A number of key Republicans who have long opposed similar comprehensive reform efforts said their concerns have not abated.

Rep. Lamar Smith (Tex.), who just completed a term as chairman of the House Judiciary Committee, which oversees immigration issues, said in a statement that “by granting amnesty, the Senate proposal actually compounds the problem by encouraging more illegal immigration.”

Republican Sens. Jeff Sessions (Ala.) and David Vitter (La.), who had helped lead efforts to scuttle comprehensive immigration legislation in 2007, despite its support from President George W. Bush, came to the Senate floor to say they have deep reservations.

Particularly problematic for the bipartisan group was a statement from Sen. Mike Lee (R-Utah), who had participated in some of the gang’s early negotiations. It indicated that he could not sign on to the final product because it contemplates a “policy that will grant special benefits to illegal immigrants based on their unlawful presence in the country.”

But Republican leaders greeted the proposal with more encouragement.

Boehner — who has said that Congress must deal with immigration this year — said he welcomed the proposal and looked forward to reviewing it.

Senate Minority Leader Mitch McConnell (R-Ky.) praised the group for its “hard work” and called for an open Senate process to review any legislation that results.

Election leads to shift

The dramatic reversal in Republican opinion on the emotional issue can be traced directly to November’s presidential vote, in which Obama won the support of seven in 10 Latino voters, according to exit polls.

“Elections,” McCain said Monday to explain what had changed within his party. “The Republican Party is losing the support of our Hispanic citizens. And we realize there are many issues in which we think we are in agreement with our Hispanic citizens, but this is a preeminent issue with those citizens.”

The framework drew praise from both the U.S. Chamber of Commerce, a key business lobby, and the AFL-CIO union.

A coalition of immigration advocates announced plans Monday for a major rally in support of comprehensive reform April 10 in Washington, an event designed to “put a face” on the nation’s 11 million illegal immigrants.

At a news conference, the group, composed of labor and faith leaders as well as Hispanic, Asian and African American activists, reacted enthusiastically to the bipartisan group’s principles.

David Nakamura and Ed O’Keefe contributed to this report.