WASHINGTON -- Sen. Marco Rubio (R-Fla.) ruled out becoming his party's vice presidential nominee in 2012 and offered the Republican presidential primary field some advice about dealing with the thorny issue of immigration Wednesday. He refused, however, to weigh in on the growing number of GOP candidates who are spurning a Univision debate because of a controversy surrounding his own family.

Speaking at the Washington Ideas Forum at the Newseum in Washington, D.C., Rubio said he is "not going to be the vice presidential nominee" when moderator Major Garrett, a congressional correspondent for the National Journal, asked if he was interested in the job.

"I'm not focused on that; I'm focused on my job right now. And the answer's probably going to be no -- The answer's going to be no," he said, adding that he had to correct himself because he didn't want to be seen as leaving the door open. Rubio has offered similar answers in the past, but no one seems to believe him and he is still consistently asked about his prospects.

Garrett also brought up the fact that five of the Republican presidential candidates have said they will boycott a proposed debate hosted by Spanish-language network Univision due to allegations that the network unethically pursued a story about Rubio's family, proposing to soften the piece if the senator appeared on its Al Punto show.

"The whole thing is something I really don't even want to comment on ... I know you have to ask, but I really don't want to address the whole issue. I really don't want to give that thing any oxygen," Rubio said when asked about the controversy on Wednesday.

Rubio also offered his party a cautionary note on immigration, saying it had to be careful not to focus primarily on targeting undocumented immigrants.

"We cannot be the anti-illegal immigration party. We have to be the pro-legal immigration party," he said. "We have to be a party that advocates for a legal immigration system that's good for Americans, good for America and honors our tradition both as a nation of immigrants and as a nation of law."

Texas Gov. Rick Perry (R) has taken heat from many of his fellow Republicans for signing a law in 2001 to provide in-state tuition to some undocumented students. Fellow presidential candidate Mitt Romney, a former Massachusetts governor, has likened Perry's position to the one held by President Obama and other Democratic leaders.

In 2003, as a member of the Florida state legislature, Rubio also backed legislation -- which ultimately failed -- to provide in-state tuition rates to some undocumented students.

Rubio refused to take either Perry or Romney's side on the issue, telling reporters after the event, "Rick Perry had a bill in Texas. We had a different bill in Florida."

He said, as he has in the past , that he does not believe all undocumented students in the United States should receive in-state tuition at public colleges and universities, arguing that there should be exceptions for young people who are in the country without documents -- through no fault of their own -- and are outstanding students.

"There are instances of young people who have something to contribute to America's future, and I believe the vast majority of Americans would like to be able to accommodate them. My greater point, which I hope wasn't missed, was that it's become harder and harder to do that as this issue's gone unresolved, and people have become less supportive of those measures," he said.

Rubio, like Perry , doesn't back the federal DREAM Act, which would provide a path to citizenship for undocumented immigrants who either attend college in the U.S. or join the U.S. military. Many immigration activists have also been disappointed that Rubio has tacked more to the right and shifted away from some of the relatively moderate positions he took while in the Florida legislature.

At the Ideas Forum, Rubio insisted that his positions have been consistent and what has changed is the political environment.

"I've been consistent in saying that while I think states have a right to do these policies that may touch upon immigration, I don't think that's the best way to do it," said Rubio in his remarks. "I've consistently said that I believe that immigration has to be addressed at the federal level in order to be solved."

Rubio also said his recent comment that programs like Social Security have "weakened us as a people " was misunderstood.

"The speech was actually a very strong defense of the proper role of government," he said, adding that government programs are "intended to supplement the things that we already did as a people, not replace it."

"In many communities -- and not necessarily the entitlement programs but some of the other programs that government is involved in -- the mindset has set in that somehow because we pay our taxes, it excuses us from our individual responsibilities as a neighbor, as a family member, to help those who are less fortunate," he added. "The bigger problem, however, is that these programs are created without any thought to how we are going to afford them in the future."