Transcript for 'This Week': Sen. Marco Rubio
Now our closer look at Florida senator Marco Rubio. This week, the gop star making what could be his biggest move yet toward a run for the white house, including a key stop in New Hampshire. Jon Karl was there with him. What is going on, senator? Good to see you. Welcome to New Hampshire. We caught up with Marco rub CEO in Manchester, New Hampshire. His first foray to the first in the nation primary state since the presidential election. Likely to be the first of many. Rubio is doing everything he needs to do to prepare for a presidential run. Campaigning for republicans across the country. Hiring national staff. Raising lots of money. And writing a book on his vision for America. It seems obvious. You're moving closer to running for president? I have openly said in the past it is something I'll consider at the end of this year. I'll look at a number of factors. Personal factors. But also, whether I could best promote this message and actually put in place these ideas that I want to see put in place, whether I could best do that from the presidency or the senate. Reporter: If he decides to run, there is no backup plan. The day he announces he's running, he would announce he's not seeking re-election to the senate. If I decide to run for president, I will not have an exit strategy to run for president. You want to be the president of the United States, you run with everything. You don't run with an eject button in the cockpit that allows you to go on an exit ramp if it doesn't work out. Reporter: Do you think you're ready to be president? I do. But I think that's true for multiple other people that want to run. I'll be 43 this month. I have served now in public office for the better part of 14 years. Most importantly, I think a president has to have a clear vision of where the country needs to go and clear ideas about how the get it there. I think we're very blessed in our party to have a number of people that fit that criteria. Reporter: But you think you're ready? You think you're qualified, have the experience, if you make that decision? I do. I think our party is blessed to have a number of people in that position. Whose vision is the one that our party wants to follow? Senator Marco Rubio! Reporter: Just over a year ago, an early front-runner. Young, hispanic, a tea partier. Who could appeal to moderates. The reblican savior, on the cover of "Time." But his star has faded some. In a poll he led last year, he's now tenth. Behind even Donald Trump. What's happened to Marco Rubio? It's probably the "Time" cover jinx. Just like the "Spots illustrated" jinx. I don't know. Polls are everywhere. You decide to run for president, there will be a campaign. In that campaign, you'll interact with voters. Explain where you stand. Those Numbers can change. One way or the other. The miracle of America is still alive. Reporter: He took a beating for conservatives over immigration, working with democrats like chuck Schumer to pass a bill last year in the senate that beefed up border security but also provided a path to citizenship to many of the 12 million illegal immigrants now here in the U.S. You gave a big speech in the republican spring meeting. You didn't talk about immigration reform. Didn't come up in your speech. Have you given up? No, I didn't talk about Libya. Ukraine. I didn't talk about other elements that are important. There's a lot of issues going on in the country. Immigration is not at the forefront. I remain convinced we can do something serious about the imfwrags probl immigration problem in this country. And the party? We're not going to grant blanket amnesty to 12 million people. We're also not going to round up and deport 12 million people. Reporter: Lately, he spends more time talking about the attack on the U.S. Consulate in benghazi, Libya. There have already been 13 congressional hearings on the attack. This week, house republicans launched a new special committee to investigate further. You have had several investigations in the congress. The administration has its investigations. Do we need another committee investigating? No one's been held accountable. Who has been held accountable for what happened in benghazi? This administration doesn't worry as much about what to do as what to say. They decided to mislead the American public and the families of the victims. As to exactly what happened. You have the republican party raising money off this investigation. Is that appropriate? I would prefer we focus not on the fund-raising or in the political elements. I think it takes away from the reality of how serious this is. How big a problem is this for Hillary Clinton? I'm sure she'll brag about her time in the state department. She'll have to be held accountable for the failure. Whether it's the failed reset with Russia or the failure in benghazi that actually cost lives. What grade you to give her as a secretary of state? I don't think she has a passing grade. You think she has an "F"? If you look at the diplomacy pursued during her time in the state department, it's failed everywhere. If she's going to run on her record of secretary of state, she's going to have to answer for its failure. Reporter: This week, the white house issued a report on the dangers of climate change. Climate change is affecting Americans, all across the country. Miami, Tampa, most affected by climate change. So putting aside your disagreement with what to do about it, do you agree on the science on this? How big a threat is climate change? I don't agree with the notion that some are putting out there including scientists, that somehow, there are actions that we can take today that would have an impact. Our climate is always changing. They've chosen to take a handful of decades of research and say it is now evidence of a longer term trend that is directly and almost solely attributable to M manmade activity. Let me get this straight. You do not think that human activity, the production of Co 2 has caused warming to our planet? I do not believe that human activity is causing dramatic change to our climate the way the scientists are portraying it. I don't think the laws they propose we pass will do anything about it, but destroy our economy. Reporter: It's talk like that he hopes will appeal to the conservatives. For "This week," Jonathan Karl, Manchester, New Hampshire.
This transcript has been automatically generated and may not be 100% accurate.