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Newt Gingrich acknowledged Sunday that his campaign is "operating on a shoestring," as he signaled he is preparing to transition from candidate to surrogate in anticipation of Mitt Romney winning the nomination.

While not throwing in the towel just yet, the former House speaker spoke frequently in past tense about his presidential bid in an interview on "Fox News Sunday." He said he wants to continue to try and influence the party platform, but said he's already discussed with the Republican National Committee how he can best help the nominee defeat President Obama if it's not him.

Romney, he said, "is far and away the most likely" nominee. Looking back on the race, Gingrich said he has "no regrets" -- he became visibly emotional as he discussed on Easter Sunday how his faith helped him through the campaign.

"I'm glad I did this," Gingrich said of his decision to run, calling it "the right thing for me to do."

Gingrich spoke openly about his campaign's money troubles. He said the campaign has had to dip into personal funds -- "a little bit, but not dramatically" -- and that the campaign is "slightly less" than $4.5 million in debt.

"We owe much more than we wanted to," Gingrich said. He explained that the Florida primary in late January "got to be a real brawl" and that his campaign "tried to match Romney."

Gingrich lost that race, and so far has won just two primary contests -- in South Carolina and Georgia.

Gingrich said his campaign won't "go broke" and that he'll raise money after the election in order to pay off his debt.

Though Gingrich and Romney throughout January engaged in some of the most personal attacks of the presidential primary campaign, Gingrich said Sunday that the two are at peace with one another.

"I hit him as hard as I could, he hit me as hard as he could -- turned out he had more things to hit with than I did," Gingrich said. "That's part of the business."

Gingrich said that if Romney wins 1,144 delegates and clinches the nomination, he will do "everything I can" to support him going into November.

"We are absolutely committed to defeating Barack Obama," he said. "I will work as hard for (Romney) as I would for myself."

He said he's already spoken with RNC Chairman Reince Priebus about how he can help going into November. "Beyond that ... I'll go back to a post-political career," Gingrich said.

Still, he said supporters are urging him to stay in.

"I do think there's a desire for a more idea-oriented Republican Party," Gingrich said.

Gingrich said he's seeing a "great response" in the upcoming primaries for Delaware and North Carolina, and will "see what happens" in those two states. Despite his comments Sunday, the candidate had recently told The Washington Post that "nothing" could get him out of the race quite yet.

Gingrich said he wants to campaign for changes in the party platform -- namely, to push for domestic energy production, to "stand up very firmly for religious liberty" and to reform the Social Security system.

Romney is leading the field with 660 delegates, according to the Associated Press tally. Rick Santorum is trailing with 281, followed by Gingrich with 135 and Ron Paul with 51.