If Republicans hope to save their party from long-term minority status, they should do what I’ve been doing for the past two years: study the career of Jack Kemp.

I’ve been doing it as an oral history and biography project. They should do it as a survival mechanism. Or, better, as a way to build a party that can speak to a majority of Americans.

As opposed to 2012 GOP presidential candidate Mitt Romney, Kemp — the Buffalo Bills quarterback, New York congressman, original sponsor of supply-side economics, Housing secretary and 1996 GOP vice presidential candidate — believed that Republicans could and should go after every voter, regardless of race or income or even union membership.

Romney turns out to have been a total cynic. When he was caught in September saying privately to donors that Republicans had no chance of winning 47 percent of voters because they were “dependent on government” and thought of themselves as “victims,” he distanced himself from his own words, calling them “totally wrong.”

But then, in a post-election private talk to donors, he blamed his loss on “gifts” that President Barack Obama had given to various interest groups. He clearly meant what he said in September — that politics is just a bidding war.

Kemp was the opposite: a thoroughgoing idealist who exuded optimism and believed the GOP could win majorities by fostering hope, growth and opportunity for everyone.

He was so idealistic, in fact, that he genuinely believed that by producing sustained growth and prosperity, the GOP could once again become “the party of Lincoln,” the natural political home of African-Americans. That was unrealistic, but if anyone could have cut into Democratic dominance among blacks, it was Kemp. As a football player, one quip went, “Kemp showered with more African-Americans than most Republicans have ever met.”

A self-proclaimed “bleeding heart conservative,” Kemp sponsored enterprise zone legislation with Democrats to eliminate taxes in poverty-stricken neighborhoods, to attract investment and jobs.

He visited homeless shelters as a first order of business as Housing secretary, walked the streets of Los Angeles after the city’s 1992 riots and insisted on campaigning in ghettos and barrios during the 1996 campaign as Bob Dole’s vice presidential candidate.

In 1994, he denounced California’s Proposition 187, which would have denied government benefits to illegal aliens, and he advocated a comprehensive immigration overhaul to the end of his days. He died in 2009.

Even if there was no way for Romney to win more than 6 percent of black votes against Obama, a Kemp-like platform could have saved him from a 44-point loss among Latinos and a 47 percent loss among Asian-Americans.

As Republican pollster Whit Ayres wrote in his post-election analysis, “the handwriting is on the wall. Until Republican candidates figure out how to perform better among non-white voters, especially Hispanics and Asians, Republican presidential contenders will have an extraordinarily difficult time winning presidential elections from this point forward.”

Republicans are searching furiously for ways to get right with Hispanics after Romney’s “self-deportation” self-immolation. Kemp’s example offers a path. Some also are furiously denouncing Romney’s “gift” analysis.

Louisiana Gov. Bobby Jindal’s response sounds especially Kempian. “We need to get two messages out loudly and early,” he said. “One, we are fighting for 100 percent of the vote, and secondly, our policies benefit every American who wants to pursue the American dream. Period. No exceptions.”

That’s a good first step, but most Republicans have yet to find a way to sell conservative economics as an opportunity engine.

In his time, Kemp led his party away from an austerity politics focused on balanced budgets, lower spending and higher taxes toward growth politics based on permanent tax rate cuts.

He modeled his 1976 tax bill on President John F. Kennedy’s 1963 proposals and adopted Kennedy’s “a rising tide lifts all boats” slogan.

Kennedy’s measure, enacted after his assassination, lowered top tax rates from 91 percent to 70 percent. The Kemp-Roth bill, adopted and pushed through by President Ronald Reagan, lowered the rate from 70 percent to 50 percent. And, in 1986, a Reagan tax reform bill backed by Kemp lowered the rate to 28 percent and eliminated dozens of breaks and deductions.

America’s growth problems are different today than they were in Kemp’s era. “Stagflation” — simultaneous high inflation and unemployment — were the problem then. Now it’s high unemployment and staggering debt.

Today, Kemp surely would favor drastic tax changes to cut rates and eliminate the loopholes drilled into the tax code since 1986.

He was never much in favor of cutting entitlements, but I’d guess that, like his former intern, Rep. Paul D. Ryan, R-Wis., he’d favor reining them in to preserve social safety nets without encouraging dependency.

Kemp was never a believer in deep domestic spending cuts, either. Some of that needs to happen, but growth also requires spending on education, infrastructure and research.

The GOP today has a demographic problem, a messaging problem and — most of all — an attitude problem. The Kemp model could solve them all. He really believed in creating an opportunity society for everyone.