that dig about the K Street Project and call out Rick Santorum on his not-so-distant past:

TAPPER: Good morning, everyone. George Stephanopoulos has a well-deserved morning off. We're now just over one week away from the crucial Michigan primary. Michigan is Mitt Romney's home state, where his dad was governor. And both the Romney and Santorum camps consider the contest there to be a potential game-changer in this bitterly fought Republican nomination battle.

To discuss that fight and more, key Romney-backer and the Republican nominee from four years John McCain joined us just a few moments ago from Afghanistan.

(BEGIN VIDEOTAPE)

TAPPER: Senator, I'm going to get to international relations and foreign policy in a second, but the news this week has been dominated by politics. And, in fact, you've become part of the conversation. I want to play Rick Santorum in Columbus, Ohio, yesterday, talking about Mitt Romney's leadership of the Salt Lake City Olympics.

(BEGIN VIDEO CLIP)

SANTORUM: He heroically bailed out the Salt Lake City Olympic Games by heroically going to Congress and asking them for tens of millions of dollars to bail out the Salt Lake -- John McCain called it potentially the worst boondoggle in earmark history. Does the word "hypocrisy" comes to mind?

(END VIDEO CLIP)

TAPPER: Does the word "hypocrisy" come to mind, asks Senator Santorum. Well, does that word come to mind? Because Senator Santorum is right. He did request that money as head of the Olympics. You did criticize it. And now Mitt Romney is criticizing Rick Santorum for earmark spending. What's your reaction?

MCCAIN: Well, my reaction is that I, of course, oppose earmarks, and I've opposed them of all kinds. All I wanted them to do was go to Congress and go through the normal process of authorizing and then appropriating. I certainly wanted to save the Salt Lake Olympics, as most other Americans did.

Ooo, take that, Rick Santorum!

Mr. Santorum voted for things like the Bridge to Nowhere, zoos in Philadelphia, and was one of the more blatant defender of earmarks, which my friend, Senator Tom Coburn of Oklahoma, says is the gateway drug to corruption. And he engaged in it. He defended it. He was in this K Street Project, which led to corruption, more corruption, and eventually members of Congress ending up in jail. Of course, I opposed an earmark. But if they had gone and authorized it, I would have supported it, because I believe that the Olympics was very important to the United States of America.

Nice comeback, Johnny boy! The Olympics are right up there with Mom and apple pie. Little Ricky can keep his K Street lobbyist buddies, I'll stick with AMERICA!!!

TAPPER: You endorsed Mitt Romney, but a friend of your, former Ohio Senator Mike DeWine, who endorsed you in both of your presidential runs, this weekend unendorsed Mitt Romney and endorsed Rick Santorum. DeWine said, quote, "He's just not connecting," about Romney, "I don't know what it is, but I can tell you from real people I'm talking to, it ain't getting any better." Isn't Senator DeWine touching on a real problem for Mitt Romney? Isn't he having problems connecting to voters?

MCCAIN: No, I think it's a very tough campaign, and I understand that. But the fact is that these debates and these kinds of negative campaigns have driven the disapproval ratings of all of the members up. I am still confident that Mitt Romney will succeed. I was declared dead by pundits such as yourself back in 2007 and 2008.

But, look, I respect Mike DeWine's opinion. I am confident that Mitt Romney will succeed in both Michigan and Arizona. But it's tough. And it's not beanbag.

TAPPER: Are you worried at the tenor of the campaign being such that President Obama will have a much easier time being re-elected? I've talked to a lot of Republicans who two or three months ago were very bullish on defeating President Obama and now are very, very worried that, because this race has gotten so nasty -- and, as you suggest, the negative ratings of the candidates have gone so high, he may, in fact, be re-elected.

MCCAIN: I am concerned about that, Jake. And I think there's reason to be concerned about it. I've been in very tough campaigns. I don't think I've seen one that was as personal and as characterized by so many attacks as these are. And, frankly, one of the reasons is the super PACs. And why do we have the super PACs? Because the ignorance and naivete of the United States Supreme Court in the Citizens United campaign.

We now have a -- have a casino mogul that's, what, up to about $20 million, and a lot of that money comes from his proceeds from his casinos overseas, including China. So I think it has to do with the unlimited money, and I do not believe I've ever seen campaigns characterized overwhelming by negative attacks.