Allies noted Gingrich's storied career of returning to prominence as one of the nation's leading Republican figures after crushing public defeats.
"His resilience reminds me that his greatest asset might be his durability. It reminds me of Nixon, Clinton and Reagan," said longtime Gingrich adviser Craig Shirley, referring to eventual presidents who triumphed after political defeats. "These guys have an indomitable spirit."
Gingrich rose to become House speaker in 1995 after leading the first Republican takeover of the House 40 years. But he left just a few years later under a cloud of questions about his ethics, and has used the presidential campaign to help return him to prominence within the party.
Gingrich repeated at the first of a series of Illinois stops Wednesday his promise of "getting to Tampa" for the Republican National Convention, but acknowledged the race was taking a toll.
"This is a very challenging campaign," he told about 100 people in Rosemont near Chicago. "It is particularly challenging because I am campaigning on very new ideas that are very different."
Even as he vows to press on, Gingrich has started talking almost wistfully about the campaign.
He told the AP that while he was not bothered, or deterred, by calls for him to quit the race, he was hurt by them last summer after a mass exodus from the campaign by top advisers and staff over strategy and financial disagreements.
"That was painful. That was a point where I said, 'I've been active in this party since the summer of 1960. I think it's fair to say I helped grow the Georgia Republican Party and I helped grow the national majority,'" Gingrich said last week. "I'm a genuine outsider mobilizing the American people against the Washington establishment of both parties. That's fine with me."
Associated Press writer Brian Bakst in Rosemont, Ill., contributed to this report.
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