After winning a congressional seat that had been in GOP hands since 1872 in New York’s special election, Democrats were exultant. Bill Clinton called the vote “a referendum on President Obama’s agenda for health care and on our entire progressive agenda,” and the New York Times gloated that the vote was a “setback for national conservatives.”

Those claims were made not last week, but in 2009 when Democrats won an upset victory in New York’s 23rd Congressional District — and deluded themselves into thinking the result was a bellwether for the 2010 elections. A year later, they suffered a historic shellacking at the polls — the largest turnover of seats in the House of Representatives since 1948.

Keep this in mind as you listen to Democrats boast about taking another long-held Republican seat in New York’s 26th Congressional District last week. While their demagoguery of Rep. Paul Ryan’s plan to save Medicare certainly played a role, the fact is that Democrats won the race because a faux Tea Party candidate poured $3 million into the race and siphoned off 9 percent of the vote from the GOP nominee. As Karl Rove has pointed out, despite her vicious “Medi-scare” campaign, Democrat Kathy Hochul won only a 47 percent plurality — just one point more than Barack Obama got when he lost the district back in 2008. As national referendums go, that is not terribly convincing.

This does not mean the GOP should be complacent — far from it. The New York race exposed just how woefully unprepared Republicans were for the Democratic assault on their proposed Medicare overhaul. Some have suggested Republicans should begin to distance themselves from the Ryan plan. To the contrary, the lesson of the New York special election is that if Republicans want to win in 2012, they need to stop playing defense and go on the offensive.

Why on earth have Republicans allowed Democrats to define the Ryan proposal as a plan to “end Medicare” when it is the Democrats who risk ending Medicare though a policy of neglect? Even the New York Times editorial page warned after the New York vote, “Sooner or later, Democrats will have to admit that Medicare cannot keep running as it is — its medical costs are out of control, and a recent report showed its trust fund running out of money in 2024, five years earlier than expected.”

Democrats have put forward no plan to deal with this fiscal crisis. Quite the opposite, they made it worse by taking $500 billion out of Medicare to help fund the president’s health-care law — robbing Medicare to pay for Obamacare. The time has come for the GOP to take the gloves off. When liberal groups put up an ad showing Ryan pushing Grandma off of a cliff, Republicans need to counter with an ad showing Obama, Pelosi and Reid pushing Grandma off the cliff — because that is where Medicare is headed if we follow their policy of inaction. The message should be: If we do nothing, Medicare will collapse — and millions of retirees will be left without health coverage. Democratic neglect will kill Medicare; Republicans are trying to save it.

Next, Republicans need to expand the debate. The Medicare proposal is just one element of a broader GOP plan to reduce our ballooning debt — which, in turn, is one element of a larger plan to restore economic growth and create jobs. This has been completely lost in the recent debate. Americans are concerned with 9 percent unemployment, $4-a-gallon gas, declining home values and stagnant economic growth. To win, Republicans need to point out that the Democrats’ solution to these problems — more spending and more debt — has not only failed, it is hindering our recovery. They need to explain that when countries have debt exceeding 90 percent of annual economic output — as the United States soon will have — economic growth slows by roughly 1 percent a year. Lower growth means fewer jobs. They need to point out, as Ryan did in a speech at the Economic Club of Chicago recently, that Obama’s proposal to raise the top marginal tax rate to 44.8 percent — a nearly 10-point increase — would kill even more jobs. And they need to offer a positive vision for a better way to produce economic growth and rising incomes.

Republicans on Capitol Hill understand this. That is why Ryan called his plan “The Path to Prosperity,” not “The Path to Austerity.” And that is why House and Senate Republicans both released jobs plans this month that tackle the national debt but do so in the context of restoring prosperity with pro-growth tax cuts, regulatory reform, and measures to expand trade, encourage energy exploration and reduce the cost of health care. The GOP message must be: Spending our way to prosperity has not worked. It’s time for a new approach.

If Republicans allow the 2012 election to become a referendum on the GOP plan for Medicare, Obama will cruise to reelection. But if Republicans make the election a referendum on the economic failures of Obama’s first term — and offer a hopeful alternative vision for our economy — he may not get a second.