This is a rush transcript from "America's Election HQ," April 21, 2008. This copy may not be in its final form and may be updated.

BILL HEMMER, CO-HOST: They are the two men who could haunt Obama throughout this campaign. We're talking about his former pastor, Reverend Wright, and 1970s underground terrorist, William Ayers.

• Video: Watch the interview

McCain is now stepping up his attacks pointing to Obama's, quote, "questionable" connection to Ayers, a man who was once part of a group that bombed the Pentagon and the Capitol building.

Former Pennsylvania senator and FOX News contributor, Rick Santorum is more on that. Rick, good evening to you, senator.

RICK SANTORUM, FOX NEWS CONTRIBUTOR: Hi, Bill.

HEMMER: Thank you for your time. Here is ABC News — John McCain yesterday on William Ayers.

(BEGIN VIDEO CLIP)

JOHN MCCAIN: I'm sure he's very patriotic, but his relationship with Mr. Ayers is open to question.

GEORGE STEPHANOPOULOS, ABC HOST: Why?

MCCAIN: Because if you're going to associate and have as a friend and serve on a board and have a guy kick off your campaign that says he's unrepentant, that he wished he bombed more.

(END VIDEO CLIP)

HEMMER: Senator, he offered that without prompting. Is this fertile ground for John McCain?

SANTORUM: Absolutely. This is a relationship with someone who, you know, who hates America. Sound familiar? Someone who wished he could do more damage to America, and has really contempt for our country, and he has a relationship with him. He works with him, and he didn't work with him when he was eight years old. He worked with him in the last few years when he knew all about his history and he knew about his continuing, you know, affirmation of that history that it was the right to do.

HEMMER: Just to be accurate on that one, when he was running for state senator in Illinois, it was, what — 12 years ago, right? 1996, there's a fund-raiser that was put together in his hometown in Chicago and that's what you are referring to, right?

SANTORUM: Right, I'm saying — it was in his adult life. It wasn't when he was 8 years old which he tried to pawn off in the debate the other day. The fact of the matter is that he has these relationships. It begins to paint a picture. He's used this analogy as he did with Tom Coburn, which I thought was a remarkable analogy, similar to what he used in his speech in Philadelphia where he analogized the Reverend Wright to his grandmother, as both being, you know, having problems with race.

These analogies don't work. You can't - they're not moral equivalents. The bottom line is these two people say a lot about who Barack Obama is and they are informing the American public at a very critical time, and I think, as a result it's slowing down his momentum certainly around the country.

HEMMER: Keep on Pennsylvania, your home state, this vote tomorrow. If he loses big, is this the reason why, Reverend Wright and the small town comments or do you get a sense of teflon around Senator Obama at this point?

SANTORUM: Yes. I think he is going to lose. I think he's going to lose by a fairly significant margin, and the biggest reason he's going to lose is because of what Pennsylvania is. Pennsylvania is a blue-collar, a working class, you know, state with its older, it's - you know, seniors that turn out in big numbers.

This is very — we're impressed. We have never been in this situation having such attention paid to us. The seniors are going to come out. That's going to help Hillary. That's the reason she's going to do very well in this race. I don't think these comments are going to be as much as people pretend them to be at this point.

HEMMER: Thank you, senator. Rick Santorum. Let's talk again, OK?

SANTORUM: Thank you.

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