RUTHFULLY YOURS

House Republicans have thrown a grenade in the entitlement debate. Budget Chairman Paul Ryan bravely did what few—if any—politicians have done before. He issued a 2012 budget that forthrightly confronts the entitlement crisis. Politicians have shrunk from this debate for decades, and there were plenty of Republicans who would have been happy to continue doing so. Mr. Ryan has fundamentally shifted the national discussion.

That, believe it or not, will be the easy part. Having reset the debate, the Republicans must now win it. History holds some pointers and some warnings.

In some regards, the GOP has more going for it now than in recent years. The Obama years have sobered the country; deficits and debt are soaring and public attention, as evidenced by the midterm elections, is focused on fiscal matters.

The GOP has also been lucky in having Mr. Ryan as its entitlement spokesperson. Washington has its fair share of slick pols and policy geeks, and that Mr. Ryan is the latter has proved an asset. The Washington press corps doesn’t much like conservatives or their ideas. But it has a soft spot for elected officials who tackle unpopular causes. Its coverage of the plan is proving more honest than at times past.

But even if this coverage continues, Republicans would be wise to take away a few lessons from past entitlement fights. First is the importance of unity. A handful of years ago, George W. Bush had the courage to broach Social Security reform. That effort was killed by his own party, which fled for the political hills.

That outcome seems less likely with today’s House GOP and the many freshmen Republican who campaigned on fiscal sanity. Then again, that crowd has so far proved far more interested in short-term symbolic fights like the debt ceiling than in substantive reform. Some Senate Republicans have seemed comfortable sitting back to let the House take this on. And yet Democratic attacks will only intensify. If the GOP cracks, it is in trouble.

The unity point counts too for 2012 presidential hopefuls. The Ryan plan ought to be seen as a litmus test for a crowd that has yet to distinguish itself. The putative GOP candidates have proved very good at grousing about elected Republicans from the sidelines—pushing Congress to get “tougher.” Well, Mr. Ryan got tough, and on one of the biggest questions of the day. Any Republican candidate who now fails to at least embrace Mr. Ryan’s leadership and approach—if not all his plan’s specifics—deserves to be disqualified from serious consideration.

Unity allows Republicans to accomplish something else vital to winning this debate: going on offense. The reform proposal is now out there, and the only question is who will define it. Will Republicans present it as a positive, reformist, growth-oriented agenda, or sit back and parry Democratic arguments that they are—as new DNC Chairman Debbie Wasserman Schultz said—sending granny into a “death trap”?

Here too, a past entitlement debate offers guidance. The Republicans won welfare reform in the mid-1990s not solely on the argument that welfare was too costly (though it was). They won by presenting reform as enlightened governance that gave states more flexibility and empowered welfare mothers to begin taking control of their lives.

The Ryan plan offers the same opportunities. Republicans have the ability to present Medicaid reform as the opportunity for states to engage in flexible new ways of offering better health care to their poor. On Medicare, millions of Americans are already familiar with private health-insurance options that give them control and choice. ObamaCare provides the GOP a useful comparison. And if the party is very smart, it wraps this into a growth agenda that emphasizes a future, more prosperous America.

Going on offense requires something else: member education. Here too history has a lesson. The nation might not be living under ObamaCare today had Republicans early on embraced health-care reform and educated themselves and the public. Members today need to understand Medicare and Medicaid; they need to understand Mr. Ryan’s proposals; they need to be able to coherently fold this into the broader budget and tax issues. The only thing as bad as not rallying behind Mr. Ryan’s reform will be rallying behind it badly.

One last thing Republicans need to do: know when to pass to Mr. Obama. There is perhaps no lesson from entitlement-reform history bigger than this. It takes a president to make it happen. The GOP needs to aggressively promote its plan, and just as aggressively let it be known that it is Mr. Obama’s move now. Republicans cannot remake government from the House of Representatives alone, and giving the public that impression would be a mistake.

Yes, Republicans showed great courage putting out the Ryan plan. Now comes the hard part.

Write to kim@wsj.com