Good news for a politics-weary nation: Come May 24, the debate over the Paul Ryan budget reform plan will be over—almost before it began. Democrats win. Republicans lose. Long live blowout entitlements.

That, at least, is the narrative being cast on the upcoming special election in New York’s 26th congressional district. GOP candidate Jane Corwin had been handily ahead until several weeks ago, when Democrat Kathy Hochul began attacking her for supporting Mr. Ryan’s plan. Polls have tightened, and Democrats and the media are now pitching the race as a “referendum” on GOP hopes to cut spending and reform entitlements such as Medicare. A Hochul victory, goes the line, will prove the Ryan plan is a bust even with conservative voters.

Fascinating, if utterly untrue. In their drive to nationalize this story, Democrats and the media are deliberately ignoring the real (if mundane) reasons why the Corwin campaign is struggling—namely, GOP infighting that has allowed a third-party candidate to siphon votes. New York 26 does offer the GOP some important lessons about the entitlement debate—just not any that Democrats are flogging.

The New York seat opened earlier this year, when Republican Rep. Chris Lee resigned in the wake of embarrassing emails and photos. The district ought to be an easy GOP win; it encompasses conservative areas of western New York that Mr. Lee last won with 74% of the vote.

Instead, conservatives are split. New York requires parties to pick candidates for special elections. The GOP couldn’t have held a primary even if it wanted to, though try telling that to fractious tea party voters who remain skeptical of the Republican establishment.

In this case, the GOP at least chose a nominee, Mrs. Corwin, who in 2008 had won a conservative primary and a state Assembly election, and who boasts name recognition and the ability to self-fund. Yet her nomination has inspired resentment, much of it stoked by David Bellavia, a veteran who bowed out in a bitter 2008 primary against Mr. Lee, and who expected to get named this time. When Mrs. Corwin was chosen instead, he launched an independent bid to get on the ballot, the failure of which (over a paperwork snafu) further infuriated his grass-roots supporters.

All of this provided an extraordinary opportunity to one Jack Davis. Who he? Ah. A 78-year-old businessman who will be making his fourth attempt to win the seat. The first three times he ran as a Democrat, boldly praising Nancy Pelosi. Sniffing a new opportunity, Mr. Davis this time submitted the requisite 3,500 signatures necessary to get on the ballot and then told the Board of Elections to officially list him as the, uh, “Tea Party” candidate. No joke.

No tea party claims him, and Mr. Davis is anything but conservative. But his self-proclaimed tea party tag—and his campaign as an “outsider”—has earned him the disaffected vote. He’s been helped by Mr. Bellavia, who endorsed him in an angry slap at the GOP. He’s also been helped by Mrs. Corwin, who was painfully slow to recognize him as a threat. Recent polls show Mr. Davis pulling nearly 25% of the vote, much of it siphoned from Mrs. Corwin. This—not the Paul Ryan plan—is the main explanation for why Mrs. Hochul is narrowing the polls.

Not that you’d know this from reading, say, the New York Times, which this week ran a story that never once mentioned Mr. Davis, while attributing Mrs. Corwin’s troubles to Mrs. Hochul’s seizure of “public uneasiness over the House Republicans’ plan to overhaul Medicare.” This is ripped straight from the Hochul campaign—which has cleverly used the “referendum” line to gin up grass-roots money and party support.

To be clear, Mrs. Corwin has voiced her support for Mr. Ryan’s budget. And Mrs. Hochul is making that a centerpiece of her (false) attacks on Mrs. Corwin. It is also the case that this is having some effect, with private polling showing voter “uneasiness” over the Ryan plan. The question is why.

One answer is that Mrs. Corwin, despite initially voicing support for the Ryan plan, has largely ducked further debate. She’s run no ads countering the Hochul claims and has made little effort to explain the Ryan reform. She’s left the field to the Democrat, allowing Mrs. Hochul to make the twin, deadly accusations that Republicans intend to “cut taxes” for the “wealthy,” which will necessitate the “end” of Medicare.

This is the lesson of NY 26 for Republicans. Having boldly jumped into the entitlement debate, the party had better be willing and able to define its reform—or the other side will do it for them. The risk was never Mr. Ryan or other veteran Republicans, who capably explained the plan at recent town halls and came away with largely positive experiences. The risk was always the hundreds of less-seasoned Republican members and candidates, who may be eager but who remain unequipped to have a rousing Medicare debate.

The GOP should thank Democrats for spotlighting this problem, so Republicans can think through the political challenges. New York 26 isn’t a referendum on the Ryan plan. But it is a flashing “Get Your Act Together” sign for 2012.

Write to kim@wsj.com