President Barack Obama began rallying supporters Tuesday to back his immigration-overhaul plan, while Republican Sen. Marco Rubio worked to persuade conservatives in his party to support a similar bipartisan plan that has gained momentum in the Senate.

Mr. Obama told supporters in Las Vegas that he was encouraged by the set of principles released Monday by eight senators. "For the first time in many years, Republicans and Democrats seem ready to tackle this problem together," he said.

President Barack Obama said in Las Vegas Tuesday his approach would benefit those who want 'to earn their way into the American story.' Reuters

But he cautioned that the path would get tougher as the legislative process advanced, and said he would release his own proposal, already drafted, if the process became bogged down in Congress.

Mr. Obama's role in the immigration debate so far is calibrated to generate excitement among supporters while trying to avoid alienating Republicans who may be hesitant to back legislation if it is too closely identified with him. "We have to pass this in a bipartisan way," said Sen. Chuck Schumer (D., N.Y.), one of the senators working on the issue. "He's giving the Republicans their space."

At the same time, Mr. Obama's 2012 campaign manager, Jim Messina, said a newly created arm of the campaign, Organizing for Action, would email the president's grass-roots backers and ask them to call members of Congress.

Mr. Obama laid out his own set of principles to guide an immigration-law overhaul, which was largely similar to the Senate framework. Both seek new border security measures, a tougher employer-verification system and a path to citizenship for the 11 million people now in the country illegally. Mr. Obama also agreed with Republicans who said newly legal immigrants shouldn't qualify for subsidies under the 2010 health-care law.

President Obama unveils his own framework for a bill before an audience at a Las Vegas high school. Laura Meckler has details on The News Hub. Photo: Reuters.

But there were key differences. The biggest: The Senate framework wouldn't allow people to qualify for citizenship until unspecified improvements in border security were met and a new system was in place to track people who arrive on legal visas.

Republicans insist on that provision, but the White House explicitly rejected it. "We're going to have a tough road ahead without that," said one GOP Senate aide.

Mr. Rubio, a member of the bipartisan group, promoted the Senate proposal Tuesday as a guest of radio host Rush Limbaugh, who a day earlier had derided it at length. Like many conservatives, Mr. Limbaugh had criticized the plan's mechanism for granting citizenship, calling it "amnesty'' for lawbreakers.

Mr. Rubio emphasized that the proposal would make citizenship contingent on stricter enforcement rules. "If there is not language in this bill that guarantees nothing else will happen unless these enforcement mechanisms are in place, I won't support it," Mr. Rubio told Mr. Limbaugh.

During a speech at a Las Vegas high school, President Barack Obama praises an immigration-overhaul plan proposed by a bipartisan group of senators, calling their efforts encouraging and prodding Congress to act. Photo: Getty Images.

By the end of the interview, Mr. Rubio appeared to have made headway with Mr. Limbaugh, who told his guest: "What you are doing is admirable and noteworthy. You are recognizing reality." The radio host questioned, however, whether Mr. Obama would go along with the principles Mr. Rubio laid out.

In reaching out to conservative Republicans, Mr. Rubio is doing something that other GOP senators backing the framework cannot. Sens. John McCain of Arizona and Lindsey Graham of South Carolina have both worked on the issue much longer than Mr. Rubio has and say similar things about it. But many conservatives don't trust them, partly because they have worked with Democrats in the past on this and other issues.

Mr. Rubio, by contrast, came to national prominence backed by the tea party. Still, as a potential 2016 presidential candidate, he is taking a risk in backing a bill that includes relief for those in the U.S. illegally. "It takes a lot of guts, someone in his position, to go on all the conservative talk shows and make the case," Mr. Schumer said of his Senate colleague.

Write to Laura Meckler at and Peter Nicholas at