Since Nov. 6, Republicans have, for perfectly understandable reasons, expressed their deep disappointment with the election results. But even in defeat something significant and positive occurred: Republicans fought Democrats to a draw on the issue of Medicare.

That was supposed to be impossible. Republicans were warned that if their nominee made even sympathetic noises about Medicare reform, it would be politically poisonous. Mitt Romney, to his great credit, ignored the warnings. He not only endorsed structural reforms for Medicare, he chose as his running mate the main congressional advocate for those reforms, Wisconsin Rep. Paul Ryan.

Steve Israel, chairman of the Democratic Congressional Campaign Committee, called Mr. Romney’s choice a “down-ballot disaster” for Republican candidates that would give the Democrats momentum in their fight to regain the House. The DCCC sent a fundraising appeal less than an hour after Mr. Ryan was officially announced as Mr. Romney’s running mate. “Yeah–THAT Paul Ryan,” the email read. “The architect of the Republican plan to kill Medicare.”

David Axelrod, the president’s senior campaign adviser, claimed that the Romney-Ryan plan would turn Medicare “into a voucher program . . . ultimately they’re going to shift thousands of dollars onto the backs of seniors and Medicare itself will be in a death spiral.” CNN political correspondent Candy Crowley said the selection amounted to “some sort of ticket death wish.”

Yet according to exit polling for the National Election Pool, the Romney-Ryan ticket carried voters age 65 and older by 17 points (58%-41%), nine points more than the McCain-Palin ticket four years ago. Among voters 45-64 years of age, Romney-Ryan defeated Obama-Biden by four points. In 2008, Obama-Biden carried that demographic by five points.

Most noteworthy, voters responded well to Mr. Ryan’s Medicare argument when positioned against the Democratic attack. In a postelection national survey by Resurgent Republic, 52% of voters agreed with the description of Mr. Ryan’s Medicare plan as one that would “preserve and protect the program,” versus 35% who agreed with the description that his plan would “end Medicare as we know it.”

In addition, a poll of Obama voters commissioned by the center-left group Third Way found that fixing Medicare and Social Security has significantly more support among liberals than is generally believed. This survey, conducted by President Obama’s polling firm, the Benenson Strategy Group, found that nearly eight in 10 Obama supporters who were surveyed believe the president and Congress should make changes to fix Medicare and Social Security, ranking those changes second in importance only to raising taxes on the wealthy. “A full 85% of the Obama Coalition listed fixing the programs as an important priority, with 48% saying it was extremely important,” according to the group.

As reporter Sam Baker wrote in the Hill newspaper days before the election, “Attacking Paul Ryan’s Medicare plan–once seen as the most potent weapon in House Democrats’ campaign arsenal–is turning out to be a dud. . . . Medicare simply hasn’t become the powerful tool that Democrats–and even many Republicans–expected.”

So how did the GOP defuse an issue that for years had bedeviled them? First of all, the candidates went on the offensive. Rather than wait for Democratic attacks, Messrs. Romney and Ryan drew attention–through speeches, ads and surrogates–to the fact that President Obama had raided Medicare to the tune of more than $700 billion in order to fund the Affordable Care Act (aka ObamaCare). This forced the president into a defensive crouch.

Second, Mr. Ryan in particular took it upon himself to speak proactively about Medicare. He explained why injecting competition into the system–just as we have done with Medicare Advantage and the prescription drug plan–would lower costs and improve efficiency.

On the campaign trail Mr. Ryan continually provided reassurance to individuals 55 and older that nothing would change for them. And he drilled home–including before an AARP audience–the point that without reforms, Medicare would go broke and collapse. The message was clear: Messrs. Romney and Ryan were the ones whose reforms would save Medicare, while doing nothing will eventually destroy it.

Fighting Democrats to a draw on Medicare–including the fact that Republicans retained comfortable control of the House–may well be seen one day as a key moment in American politics, when “Mediscare” attacks finally lost their potency. The campaign showed Republicans that it pays to deal with attacks head-on rather than run from them, that treating the American people in a mature fashion pays dividends, and that calm, persistent and well-reasoned arguments can overcome demagoguery.

Messrs. Romney and Ryan may have lost, but in the process they provided Republicans with an invaluable lesson and a blueprint for future elections.

Peter Wehner is a senior fellow at the Ethics and Public Policy Center. Messrs. Senor and Wehner were advisers to the Romney-Ryan campaign.