For the last two decades, countless Republican politicians have associated themselves with Ronald Reagan. It can link a run-of-the-mill conservative with glories past. But Paul Ryan, though a Reagan admirer, has not explicitly modeled his career on the Gipper. Instead, he frames his politics through the prism of Jack Kemp, the late supply-side congressman from upstate New York. Like Reagan, Kemp was a conservative hero, but his power base was the House of Representatives, as well as right-leaning journalists and think-tank scholars.

“As with many of us who served then, Jack, Newt Gingrich, and others always felt that the House of Representatives was the place where the country was ultimately changing or not changing,” says former Minnesota congressman Vin Weber, a longtime Ryan confidant and Kemp ally. “It’s not that other areas are not important, but we felt that over time the House was probably the best indicator of where the country would go. It is closer to the people, the battlefield of ideas. Jack Kemp recognized that, and so does Paul, whose work is in that tradition.”

As he has risen on Capitol Hill, Ryan, a seven-term House member from southern Wisconsin, has built a Kemp-like political base. He has also repeatedly avoided the temptation to seek higher office, from turning down a Cabinet post during the Bush years to deciding against a Senate run earlier this year. The House, specifically the Budget Committee, of which he is chairman, is his home. So are the conference rooms at the American Enterprise Institute on 17th Street in downtown Washington, where he makes frequent appearances. His aim, it seems, hasn’t been just winning elections, but also winning an argument about the fiscal and economic stakes – and doing it cheerfully. “Jack was always talking about the sunlit plains and the path to prosperity, and Paul is the same way, another happy warrior,” says Bill Bennett, an education secretary in the Reagan administration.

As Ryan now storms the country as Mitt Romney’s running mate, that sense of mission and echoes of Kemp’s message are everywhere. Speaking in Manassas, Va., on Saturday, Ryan heaped praise upon the man who inspired him. “I’m a person who grew up with a lot of mentors in my life,” he said. “One of the most important mentors to me was a man named Jack Kemp.”

Ryan may spread apocalyptical fiscal warnings on the trail, but his broad vision for the country is, in fact, upbeat, optimistic, and rooted in the legacy of both Kemp and Reagan, who advocated tax cuts and growth as the best path to prosperity. As Democrats attempt to define Ryan as an Ayn Rand–reading entitlement thief, Ryan is attempting to define himself in his own terms. To do that, he isn’t merely citing his legislative accomplishments, but is going back to his past, and to the supply-side thinkers.

What makes the Ryan-Kemp connection so distinct from most political relationships is how it began. Ryan was an unknown recent graduate of Miami University, in Ohio, when he first came to Washington in the early 1990s. He landed an entry-level position in the office of Senator Bob Kasten of Wisconsin, but when Kasten lost his reelection bid in 1992 Ryan was out of a job. From that point, he could have gone in various directions. K Street, another congressional staffing post, or graduate school were options. Ryan chose none of the above. He sought out a position at Empower America, a think tank run by Kemp, Weber, Bennett, and former United Nations ambassador Jeane Kirkpatrick. Climbing the career ladder was probably part of his calculus, but it likely wasn’t everything. On numerous occasions, Ryan has talked about how he sought out Kemp. He wanted to be an ideas man, not just a Beltway power broker.

“The whole Kemp family sort of adopted Paul; they saw him as someone who’d be passed Jack’s torch,” Weber says. “Paul was drawn to a lot of things at Empower America, but Jack was clearly the magnet.”

When his hometown congressional district had an open seat in 1998, Ryan decided to run for the House. He enlisted Kemp, by then his confidant, to stump for him. The silver-haired New Yorker, a former vice-presidential candidate who had shared the ticket with Bob Dole two years earlier, flew to Janesville and boosted his protégé. Kemp talked up the 28-year-old staffer’s smarts and values. Ryan won, even though his district had long supported moderate, Rust Belt Democrats.

Ryan has always credited Kemp’s lessons for that victory and subsequent wins. “How does a conservative Republican from the eighth most heavily unionized district in America — a district that voted for Dukakis, Clinton, Gore, and Obama — not just win reelection in a year when Republicans are getting trounced, but actually improve the margin of victory?” Ryan asked at a Kemp Foundation dinner in 2009. “He does it by being a Jack Kemp Republican — and winning the votes of a lot of Jack Kemp Democrats.”

Kemp’s appeal to Ryan was rooted in his policies, but Ryan also partially adopted Kemp’s gregarious, positive campaign style. “When I first met Paul, I was stunned by how technically competent he was on the budget,” says Douglas Holtz-Eakin, a former director of the Congressional Budget Office. “But he is also a great politician. He knows how to take what he knows and translate it into something that people understand.”

Of course, as Al Hunt recently observed in the New York Times, Kemp and Ryan are not identical. Ryan is much more disciplined than Kemp, who often misstepped during his ’96 veep campaign. And as Stephen Moore wrote in the Wall Street Journal this week, Kemp and Ryan “diverge” on spending, since Ryan is much more of a deficit hawk than Kemp. Both of these divergences, Moore adds, reflect the fact that Ryan and Kemp came of age in different eras. When Kemp was rising in the late 1970s and early 1980s, the debt did not loom like a black cloud over the national political debate as it does today. And at the time, Kemp’s kind of colorful, extemporaneous nature was a common political trait, whereas Ryan operates in the YouTube era, in which every utterance goes public.

But while Kemp and Ryan are of different generations, they are men of the same school. They didn’t meet because of political connections; they met because of their shared beliefs. Kemp mentored Ryan and ultimately handed the reins of the supply-side movement, at least its congressional wing, to him. Officially, Ryan may be a spokesman for the Romney platform, but at his core he remains the leader of the GOP’s Kemp caucus — the market-loving conservatives who grew up reading Robert Bartley editorials in the Journal and cheering for Kemp’s sunny, opportunity-themed speeches.

“One day, when we were at Empower America, Paul was in my office when Jack walked in,” Bennett remembers. “He reminded Paul, who was young, that Adam Smith was a professor of moral philosophy. Paul has understood that from the beginning. He often gets cast as somebody who only sees things with a green eyeshade, but like Jack, he understands how the economy is shaped by other important issues.”

A year ago, when Ryan was mulling a presidential run, I jumped into the backseat of his SUV and spoke with him about Kemp as we zoomed past the Smithsonian and the Mall. Ryan told me that he wouldn’t run in 2012 because it didn’t fit his goals as a lawmaker. What he wanted to do was stay in the House and chart new political ground. Kemp, he recalled, once told him that the best politicians weren’t consumed with ambition for a bigger title, but with idea of building a better future.

“He taught me that big ideas are the best politics,” Ryan said. “They will always be challenged, and they will sometimes be controversial, but you have to do what you think is right, what you’re passionate about, and be a strong advocate for it. If you do that, you can shift the debate in a major way. He showed me how you can do that.”

Ryan did that, and now, like Kemp in 1996, he is on a national ticket. But, he hopes, with better prospects.

* Robert Costa is a political reporter for National Review.