Erie County Clerk Kathy Hochul won a House special election in western New York on Tuesday night, a Democratic triumph in a conservative district that many regarded a referendum on House Republicans’ efforts to reform Medicare.

With 90 percent of precincts reporting, Hochul had 48 percent of the vote. State Assemblywoman Jane Corwin (R) had 42 percent, with independent candidate Jack Davis running a distant third with 9 percent.

Democrats contended that the race in New York’s 26th Congressional District — which the GOP had held since the 1960s — became competitive through their efforts tying Corwin to the House Republican budget plan that included a provision to turn Medicare into a voucher program.

That plan, spearheaded by Budget Chairman Paul Ryan (Wis.), has already been the subject of plenty of debate in Washington, where Republicans seek deep cuts and debt-reduction measures; the Medicare plan figures prominently in that effort.

But polls show that overhauling Medicare is unpopular with the public, and even while the overall budget plan has wide GOP support in the House, Senate Republicans are still discussing what to do with it as a vote looms this week. Other Republicans, including presidential candidate Newt Gingrich, have at times declined to embrace the proposal.

Corwin’s struggles in what has long been a GOP district may provide a chilling effect for Republicans who were already hesitant to embrace the entitlement reform.

Democrats ran ads about the issue early and often, seeking to overcome a significant registration disadvantage in the Buffalo-area district. In the end, that strategy appeared to have worked.

“Today, the Republican plan to end Medicare cost Republicans $3.4 million and a seat in Congress,” said Rep. Steve Israel (N.Y.), the chairman of the Democratic Congressional Campaign Committee. “And this is only the first seat.”

Even before voters went to the polls Tuesday, Republicans played down the significance of the race and particularly its relevance to the debate about Medicare’s future.

“I know this town loves to take signals from individual races. I think the best signal you can take is the 63 seats that we picked up in November,” House Majority Leader Eric Cantor (Va.) told reporters Monday.

Cantor and other Republicans cited the presence of Davis in the race. Though he previously ran for the seat as a Democrat, he ran this time on a ballot line labeled “Tea Party.” His share of the vote, Republicans contended, came at Corwin’s expense.

As for the national debate, Senate Democrats think that centrist voters in most states reject the Ryan plan to overhaul Medicare. The proposal would gave future beneficiaries vouchers with which to buy insurance on private markets.

Senate Majority Leader Harry M. Reid (D-Nev.) has scheduled a vote for later this week on the Ryan budget. At least four Republicans — Sens. Scott Brown (Mass.), Susan Collins (Maine), Rand Paul (Ky.) and Olympia J. Snowe (Maine) — have announced opposition to the bill, with all but the conservative Paul viewing the Medicare proposal as too punitive.

Reid and Democrats hope that Republicans who support the Ryan plan, which passed the House on April 15 on a party-line vote, will hurt themselves in general elections next year and in 2014. Republicans who oppose the Ryan plan may face political fallout in their primaries, Democratic aides said, pointing to the recent troubles experienced by Gingrich.

Republicans countered that they believe that voters will reward their “bold leadership” on the issue of swelling federal debt and stagnant job growth.

Republicans have had a rough go of it in recent special elections, even losing a few competitive races in the run-up to their big gains in 2010. They acknowledge that the environment isn’t as friendly now as it was in the November elections, but they say Tuesday’s election is hardly the beginning of a Democratic resurgence in 2012.

“If special elections were an early-warning system, they sure failed to alert the Democrats of the political tsunami that flooded their ranks in 2010,” Rep. Pete Sessions (Tex.), the chairman of the National Republican Congressional Committee, said in a statement.

The House seat became vacant after Rep. Christopher Lee (R-N.Y.) resigned following revelations that he had posted shirtless pictures of himself online.