Mitt Romney, who had just left office as governor of Massachusetts and was moving to the right on issues like abortion, was beginning to immerse himself in federal budget policy. Representative Paul D. Ryan of Wisconsin, who on that day in early 2007 had just become the top Republican on the House Budget Committee, was promoting a small-government libertarianism that within a few years would become Republican Party orthodoxy.
Inside the Longworth House Office Building, 15 minutes turned into an hour as the two men traded theories about how to overhaul Medicare, Social Security and the tax code, a pair of policy mavens out-geeking each other over esoterica like border-adjustable taxes. “We went deep into the weeds,” Mr. Ryan recalled in an interview.
It was the start of a on-again, off-again five-year courtship that encapsulated their party’s gradual adoption of a more conservative stance on fiscal issues, a shift punctuated a week ago by Mr. Romney’s selection of Mr. Ryan as his running mate.
His choice of Mr. Ryan had clear political overtones for Mr. Romney, who despite years of trying to win over the right was still viewed with some suspicion by many conservative leaders. But to the degree that it was a marriage of political convenience, it came about only after the two Republicans engaged in regular, substantive and previously undisclosed exchanges that by this spring had left a skeptical Mr. Ryan convinced that Mr. Romney had come to a similar policy viewpoint. The future No. 2, it turned out, was doing some vetting of his own.
Over the past 18 months, with Mr. Romney emerging as the Republican Party’s presidential nominee, the frequency and intensity of their communication deepened. Mr. Romney turned to Mr. Ryan for detailed consultations on his economic platform. Mr. Ryan made sure his Medicare proposal in the House matched up with what Mr. Romney was offering on the campaign trail.
Mr. Romney recruited several of Mr. Ryan’s top aides as campaign advisers, and the candidate’s staff members asked the congressman to review language in Mr. Romney’s planned speeches and opinion pieces, people close to both men said in interviews.
Mr. Ryan did not shy from offering pointed advice well before he was named running mate: for months, he had urged Mr. Romney to focus his campaign as much on a “a positive vision” as on the shortcomings of the Obama presidency, something Mr. Romney has since emphasized.
“A lot of substance was exchanged between them,” said Tom Rath, a longtime political adviser to Mr. Romney. “Ryan’s name came up very frequently. Those guys who were traveling with Governor Romney would say, ‘Oh, I know he talked to Ryan about this’ or ‘Ryan and he were e-mailing about that.’ ”
Even so, Mr. Ryan remained unconvinced that Mr. Romney was the right messenger for his philosophy until well into the 2012 campaign.
He took his worries about Mr. Romney public, telling The Milwaukee Journal Sentinel last summer: “I understand the knock on him. I understand the concerns. They’re legitimate.”
Friends said he had wondered aloud about the depth of Mr. Romney’s commitment to bold conservative ideas, asking colleagues whether he was “wishy-washy,” as one of them recalled.
Mr. Ryan recalled that he had wanted specifics before he was willing to deliver his endorsement and the credibility it would carry in the right wing of the party. Mr. Romney delivered what Mr. Ryan was seeking in a series of phone calls and meetings, determined to win Mr. Ryan over. Their interactions became so commonplace that colleagues recalled spotting Mr. Ryan duck into a phone booth in the House to take a call from Mr. Romney.
“What I was very surprised by was how much he and Mitt were talking, even prior to Paul endorsing him,” said Representative Aaron Schock, an Illinois Republican who is close to Mr. Ryan. “It was way beyond the perfunctory solicitations for support.”
In the course of those lengthy discussions, Mr. Ryan said, “I got a very good idea of the kind of reformer he wants to be.”
Just days before the Republican presidential primary in Wisconsin in early April, Mr. Ryan said he would back Mr. Romney, canceling a long-planned family vacation to campaign with him. (Mr. Romney held off a final challenge in Wisconsin from Rick Santorum and from that point cruised to securing the Republican nomination.)
In the interview, Mr. Ryan said there was no agreement by Mr. Romney during their talks over the vice-presidential slot to adopt the Ryan budget in its entirety as their campaign platform. Mr. Romney, while noting that their Medicare approaches are largely the same and expressing general admiration for the budget that Mr. Ryan pushed through the House this year, has hedged about elements of the Ryan plan, including the scale of its proposed spending cuts.
“He is the policy leader,” Mr. Ryan said. “He is the top of the ticket, and I joined it knowing this and being extremely comfortable with it.”
Not long ago, their partnership might have seemed unlikely. Mr. Romney had been a blue-state governor who championed a state-run health program with an individual mandate and had been willing to increase fees on residents to solve a state budget deficit. Mr. Ryan was a Tea Party hero who gave the conservative movement a detailed policy alternative to employ against President Obama’s spending and deficit increases and complex health care overhaul.
The story of how they came together offers insight into both how the Republican Party moved in Mr. Ryan’s direction and how Mr. Romney came to embrace a vision of the size and role of government that, with the selection of his running mate, will define his campaign.
“The nominee is saying: ‘I share this philosophy. It’s not enough to get elected — I want to fundamentally transform this government,’ ” said Gov. Scott Walker of Wisconsin, a Republican who became a symbol of small-government conservatism when he cut the collective-bargaining rights of unionized state workers last year.
After Mr. Romney’s quick exit from the 2008 Republican presidential primary campaign, in which he was bedeviled by charges of ideological flimsiness, he went through a period of rigorous self-examination that coincided with a sea change in Republican politics. The party’s base, inflamed by bank bailouts, the federal stimulus bill and the Obama health care program, moved rightward. The Tea Party-infused freshmen who entered the House after the 2010 elections paved the way for Mr. Ryan’s ascendancy.
Mr. Ryan was a touchstone for Mr. Romney as he tried to ensure that his policies were in sync with the spiritual heart of the party, the House Republicans.
“The one thing we did not have the last time was a link to the emerging Tea Party or the hard right, somebody who could help Mitt work through things he wanted to say that would resonate,” Mr. Rath said. “I think Ryan has been able to do that.”
Between 2007 and 2010, most of their interactions were glancing: Mr. Romney called to congratulate Mr. Ryan on election night in 2010 and to wish him luck when he delivered the Republican response to the president’s State of the Union address the next year.
But in Mr. Ryan, Mr. Romney saw shades of himself: a clean-cut numbers guy who favored the cold-eyed truths of actuarial tables over ideology for its own sake — the kind of person, friends said, he would have recruited at Bain Capital when he was chief executive.
In Mr. Romney, Mr. Ryan saw, over time, a presidential candidate as steeped in the messy minutia of policy as he was. “A classic executive,” Mr. Ryan said.
As the large and rowdy field of Republican presidential candidates sought Mr. Ryan’s counsel last year, he said, Mr. Romney quickly emerged as the most invested and engaged in the issues most important to him.
“I met with Rick Perry and Newt — all of them — Huntsman,” Mr. Ryan said. “I would tell my colleagues, ‘Romney is the one who understands this stuff.’ ”
He became comfortable enough to send Mr. Romney memos over the past few months encouraging him to focus on bolder ideas and to offer greater specificity in his proposals.
Mr. Ryan made his own concessions to the relationship. This year, he adjusted the House Republican plan for reducing the cost of Medicare to guarantee that future participants could keep a traditional fee-for-service plan, just as Mr. Romney’s plan does. “We made our plan look more like his,” Mr. Ryan said.
By the time Mr. Romney was ready to make a decision about a running mate two-and-a-half weeks ago, both men had seemed to have concluded that they would mesh well both politically and substantively.
“There was a comfort level with him organizationally,” Mr. Rath said. “They are both, in their essence, wonks.”