Rick Santorum went up to the edge of endorsing Mitt Romney this evening, but failed to pull the trigger despite many attempts by CNN's Piers Morgan to get him to say the word.

Clearly frustrated by Santorum not dancing around the endorsement of Romney, Morgan at one point said, "Spit it out."

"He's the person that is going to go up against Barack Obama it's pretty clear and we need to win this race. We need to beat Barack Obama," Santorum said about Romney.

Morgan then said, "You just endorsed Mitt Romney?"

Santorum told Morgan, he "can call it whatever you want."

Morgan then tried Santorum's wife Karen, who also took part in the interview, and asked her if she saw his words of praise of the presumptive GOP nominee as an endorsement.

"No, not at this point, no, we are working through it. We are talking about it," Karen Santorum said.

The former rival also praised Romney's speech in New Hampshire, calling it a "good speech" and saying, "He set the right tone."

"The tone was this race is about Barack Obama and his failures," Santorum said. "He's got an optimistic vision for this country and I'm very glad to see that. He painted a strong picture. It's a very clear contrast to what this president has brought this country."

Santorum said he would be meeting with Romney staffers Wednesday. ABC News reported earlier today that Santorum will meet with Romney on May 4.

The former Pennsylvania senator also said he has been hearing some of himself in Romney's recent speeches.

"I was in St. Louis at the NRA, listened to his speech on freedom and heard a lot of familiar refrains, which I was actually pleased to hear," Santorum said. "Imitation is the greatest form of flattery, and so when I hear a familiar line from another candidates that makes me feel like maybe we had an impact out there."

Morgan asked Santorum if he was holding out an endorsement for money to relieve his debt or even a cabinet post in a potential Romney administration.

Karen Santorum quickly answered, "No, we are not doing that."

"That's not what this is about," Rick Santorum said. "I mean this is about winning the election. Making sure we have the right person in the presidency, in the House and Senate."

Towards the end of the interview, Morgan again tried to get the former presidential candidate to clearly endorse Romney, or at least to admit that he already had during their back and forth. Santorum didn't say the word endorse once during the interview.

"All I said was the obvious, which is Mitt Romney is going to be the nominee and I'm going to support the nominee, whoever that nominee is, period," Santorum said.

Morgan pointed out that was Romney. Santorum answered, "Well that's what it looks like, yeah."

"If he is the nominee I'm going to do everything I can to make sure he beats Barack Obama, absolutely. That's why I got into the race," Santorum said, still choosing not to fully embrace Romney.

Morgan also asked Santorum if he would want to share a ticket with Romney.

"I'm not interested in any position," Santorum said, and wouldn't comment on whether there are any others he thought should be on Romney's vice presidential short list.

Karen Santorum said she would be "very surprised" if Romney picked her husband. She also said her favorite moment of the campaign was her husband's Iowa win. She recalled telling her children to "soak in" the moment.

Morgan at that point gave up trying to squeeze out a formal endorsement from Santorum, saying, "We'll always have Iowa."