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(CNN) —  

When Republican naysayers were mocking Donald Trump’s improbable White House campaign before the primaries started, Newt Gingrich was reading “Trump: The Art of the Deal.”

It was a pivotal part of Gingrich’s introduction to Trump – and the beginning of an almost scholarly undertaking to understand the making of the man who would go on to seize his party’s nomination for president. Months later, as the GOP prepares to coronate Trump at its convention, the former House Speaker has emerged one of Trump’s most high-profile supporters and even secured himself a top spot on the billionaire’s vice presidential shortlist.

Gingrich appeared with Trump on the campaign trail for the first time Wednesday, marveling at what the presumptive Republican nominee has accomplished as a political newcomer.

“Donald Trump has been in politics now for slightly over 12 months. It’s unbelievable,” he said at a rally in Cincinnati, Ohio.

Gingirch then proceeded to call out Ohio Gov. John Kasich, Trump’s former rival: “Your governor who is a good friend of mine, although it’s about time he gets on the Trump bandwagon!”

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At 73, Gingrich’s reemergence in national politics comes almost two decades after the pinnacle of his own career in public office. Friends and advisers to the former House speaker, who resigned from Congress in 1999 and ran for president in 2012, say he has taken a keen interest in Trump’s 2016 candidacy in no small part because he personally identifies with the businessman and his insurgent campaign.

Former Minnesota Rep. Vin Weber, one of Gingrich’s closest allies during their overlapping years on Capitol Hill, said his friend looks back over his career and views himself as a “disruptor.” Gingrich, Weber said, believes there are close similarities between the arc of his career in the House of Representatives and Trump’s 2016 White House bid.

’People dismissed’

“Remember that in Newt’s rise, people dismissed him,” Weber told CNN. “Newt was the epitome of the anti-establishment activist and he was ridiculed and laughed at by establishment figures in both parties on his way up the ladder. So he looks at Trump and that’s what he sees: He sees a guy who’s rising to the top over the ridicule of lots of people and he identifies with that.”

For Gingrich, arriving at his official endorsement of Trump in May was a months-long process.

It began with genuine curiosity. Believing that he himself was one of the last people to lead a real political revolution, Gingrich wanted to know how Trump was pulling off what most had written off as an impossible feat, one person close to the former Speaker said.

Known to friends as an insatiable reader with the intellectual appetite of a full-time historian, Gingrich pored through “Trump: The Art of the Deal,” the 1980s autobiography that details Trump’s lessons in business and real estate. Gingrich also read “Trump: The Art of the Comeback,” another autobiography released in the late 1990s after Trump’s companies had gone through bankruptcies.

From these books, Gingrich came to this conclusion: Trump is a practical man who loves to win.

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Gingrich was so fascinated by the window he believed these books offered into Trump’s worldview that he would often discuss the writings in public and even encourage political reporters to read them.

In an early January phone interview, Gingrich began the conversation with this advice for a CNN reporter: “First, let me suggest if you haven’t done it, that you ought to read ‘The Art of the Deal,’” Gingrich said. “Because it’s remarkably revealing about Trump’s style and behavior and the way he thinks.”

In another call at the end of February, just one day before Trump would win big on Super Tuesday, Gingrich offered the reporter the same instruction as the interview was winding down.

“When you finish that, you’ve got to go and get ‘The Art of the Comeback,’ which is the second book and in many ways even more interesting,” Gingrich said before hanging up the phone.

Relishing role of adviser

Those close to Gingrich say the former speaker has always relished the role of political adviser. As Trump has struggled in his transition into a general election candidate, suffering from political setbacks and self-inflicted wounds, Gingrich seems to have warmed to the idea of offering his personal guidance.

Gingrich “made the transition from outsider to governing as Speaker, and that’s clearly a Trump failing at this point,” said former Virginia Congressman Tom Davis, a longtime Gingrich friend. “A lot of people see him as a disruptor but they’re not sure he can govern.”

Trump has acknowledged that he wants to pick a partner with plenty of government experience. In addition to Gingrich, Trump’s vice presidential shortlist includes New Jersey Gov. Chris Christie and Indiana Gov. Mike Pence (Tennessee Sen. Bob Corker took himself out of the running on Wednesday, while Iowa Sen. Joni Ernst also appeared to remove herself from consideration).

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But if Gingrich were to take on a more formal role in Trump’s campaign – whether as Trump’s running mate or in another capacity – he will also undoubtedly be one of Trump’s most blunt advisers.

When the candidate sparked a political firestorm earlier this year by accusing a U.S. district judge of being biased because of his Mexican heritage, Gingrich was harshly critical.

Trump hit back, calling Gingrich’s rebuke “inappropriate.” But Gingrich remained unapologetic, as he maintained that the comments about Gonzalo Curiel were “inexcusable.”

The moment of tension between the two men proved to be fleeting. With Gingrich continuing to play the role of outspoken surrogate for Trump, sources familiar with the VP selection process said he received official vetting documents last week.

The question is whether Trump – known to bristle at criticism – could stomach another strong personality in his running mate.

“Do you want two very hot, sharp personalities on the ticket?” Weber said. “Because Newt is not a calming influence, a balancing influence. He’s a lot like Trump.”

On Wednesday, Trump vowed that Gingrich would have a role in a Trump administration.

“I can tell you in one form or another, Newt Gingrich is going to be involved with our government,” Trump said in Cincinnati. “He says I’m the biggest thing he’s ever seen in the history of politics.”