This is a rush transcript from "America's Election HQ," May 12, 2008. This copy may not be in its final form and may be updated.

BILL HEMMER, CO-HOST: First on FOX tonight: John McCain making the environment his top priority this week, pledging to fight global warming, while Democrats charge it's only an attempt to snag independent and Democratic voters.

Video: Watch the interview

Senator McCain airs a new ad about climate change in the state of Oregon. Listen here.

(BEGIN VIDEO CLIP, MCCAIN CAMPAIGN AD)

SEN. JOHN MCCAIN, R-ARIZ., PRESIDENTIAL CANDIDATE: I believe climate change is real. It's not just a greenhouse issue. It's a national security issue. We have an obligation to future generations to take action and fix it.

(END VIDEO CLIP)

HEMMER: All right. That's part of the ad.

Now, tonight, senior policy adviser to Senator McCain, Nancy Pfotenhauer, is back with us. Hello, Nancy.

NANCY PFOTENHAUER, MCCAIN'S SENIOR POLICY ADVISER: Hello, Bill. How are you?

HEMMER: I'm fine, thank you. A Republican who believes in the impact of climate change, some might think the world is spinning on a different axis, Nancy.

PFOTENHAUER: Well, you know, Senator McCain is somebody is somebody who always — he's a straight talker, as to we've said before, and when he identifies a problem, he goes after it. And this is one he embraced in about 2003. So, he's been working on it for a long time. In fact, he began his effort with Senator Lieberman and he thinks its one of the biggest challenges facing this country, and one of the biggest challenges, indeed, facing the world. And he's developed a market-based approach to solving this problem that should lower emissions, spur innovation and keep our economy strong and vibrant.

HEMMER: Nancy, what does that do in terms of a political position for McCain in this campaign?

PFOTENHAUER: Well, I think it identifies him clearly as someone who will always put the national interests ahead of his self-interests. I mean, he is not checking any political boxes. He is just identifying the most important challenges that our country faces and he's going to go after them, and no one is going to stop him. It's one of the reasons I respect him so much.

HEMMER: Nancy, I want to get to the back-and-forth between Obama and McCain in the campaigns today. That got pretty sharp, actually, about the G.I. Bill. Senator Barack Obama, listen here, on his address to McCain.

(BEGIN VIDEO CLIP)

SEN. BARACK OBAMA, D-ILL., PRESIDENTIAL CANDIDATE: I have great respect for John McCain's service to this country. I know he loves it dearly and honors those who serve, but John McCain is one of the few senators of either party who oppose this bill because he thinks it's too generous. He thinks it's too generous. I could not disagree with him more.

(END VIDEO CLIP)

HEMMER: Pretty sharp words there. Nancy, your response?

PFOTENHAUER: Oh, talk about just flagrant political pandering. I mean, that was so - that is diametrically opposed to the truth. And let me just point out that about this time last year, Senator Obama voted against $94.4 billion that would help our troops in a time of war.

Senator McCain has his own legislation, and by the way, he's largely supportive of the goals of the Webb bill. The problem is, it doesn't do enough — it doesn't it quickly enough and it does nothing to address reenlistment and retention. In fact, CBO, the Congressional Budget Office has estimated that if the Webb bill went through, we'd see a reduction in reenlistment rates of 16 percent.

The other thing that's critically different with Senator McCain's legislation is that he supports transferability of education credits, and the Webb bill doesn't do that. And what I mean by transferability, if you're a veteran and you have education benefits but you are, for some reason, unable to take advantage of them yourself, Senator McCain's legislation would allow you to give that to your spouse, give that to your child, make sure that they're allowed and your family is still allowed to benefit.

HEMMER: Nancy, not to split hairs here, but this an important here, from what I understand, McCain's proposal would take longer for servicemen and servicewomen to qualify for education subsidies. Is that it in a nutshell?

PFOTENHAUER: That is not my understanding, Bill. My understanding is that we are more generous upfront but it's a graduated scale. So that the longer you stay in the military, the more you are compensated. And that is absolutely essential for retention.

HEMMER: All right. One of the many issues we're going to get into over the coming weeks and months ahead, OK? Nancy Pfotenhauer, good to have you on tonight, all right? Come on back.

PFOTENHAUER: Thank you, Bill.

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