Updated: 9:16 p.m.

It is a special election that was never supposed to be this close. But outside groups have begun pouring money into New York’s 26th district, a conservative region near the Empire State’s western border that has become an unlikely battlefield in a new age of political influence.

American Crossroads, the outside group developed in part by Karl Rove little more than a year ago, dropped a bomb Tuesday. Two weeks before voters head to the polls, the organization dumped $650,000 into the race to reserve two weeks of broadcast and cable television advertising in the Buffalo and Rochester media markets. Crossroads released an ad Tuesday night that targets Jack Davis, a former Democrat running on the “Tea Party” ballot line and complicating Republican Jane Corwin’s path to victory.

A handful of public and internal polls suggest that Democrat Kathy Hochul and Corwin are knotted in a tight race. And while the candidates themselves have poured millions into the contest -— both Davis and Corwin are independently wealthy — Crossroads’ investment could produce a flood of outside cash to influence a special election that few took seriously a month ago.

“This may turn into an arms race,” one Democratic strategist said.

Indeed, less than five hours after Crossroads’ intentions became public, the Democratic Congressional Campaign Committee decided to place a $250,000 media buy in the district, according to another Democratic operative.

The DCCC had already been funneling money and resources to its nominee as quietly as possible, fearing that a more public role might persuade Crossroads and its conservative allies to jump in sooner.

“We have been very active behind the scenes,” DCCC spokeswoman Jennifer Crider said. “It would have been irresponsible for the DCCC to highlight the race early on when these outside groups would have been there sooner.”

In addition to providing research, communications and political support, the DCCC helped raise $50,000 for the Hochul campaign and spent the maximum coordinated limit of $47,000, according to Crider.

But Crossroads can do much more.

Created in the wake of the Supreme Court’s Citizens United v. Federal Election Commission decision in 2010, the conservative group has quickly become a national force, fueled by anonymous donations that it hopes will exceed $120 million this cycle. In some ways, Crossroads is doing the heavy lifting that would have traditionally fallen to the National Republican Congressional Committee.

It’s still unclear whether the NRCC will devote significant resources to an independent media buy in the district, where it has been providing Corwin logistical support for months. The committee’s options are limited because of $8 million in unpaid debt from a successful 2010 cycle. And Crossroads’ deep pockets mean that the NRCC might not have to do much.

The DCCC, also struggling to pay off an $8 million debt, is in a more difficult position, especially given that the seat is likely to disappear by 2012 as the result of redistricting.

Outside groups such as Crossroads mostly did not exist on the Democratic side until very recently. And it’s unclear whether organizations such as American Bridge and House Majority political action committee, still in their infancy, have the resources to counter the Crossroads buy.

Roll Call has learned that House Majority PAC, a newly formed Democratic ally that discloses its donors but accepts unlimited donations, will likely make a decision by Friday on whether it will play in the special election.

“John Boehner, Karl Rove, and the right are clearly in full panic mode in what should have been a slam-dunk for them in the special election in upstate New York,” House Majority PAC spokesman Ryan Rudominer said.

But even if House Majority jumps in, it’s not expected to have anywhere near the available resources as Crossroads. That could help explain the DCCC fundraising email that went out Tuesday afternoon.

“Karl Rove’s swift-boat group just bought a huge slate of attack ads totaling hundreds-of-thousands of dollars. Even Boehner himself made a last minute trip to the district yesterday,” DCCC Executive Director Robby Mook wrote, calling on supporters to help raise $150,000 by midnight. “They know losing a Republican district like this would be a shocking rebuke to their radical agenda and 2012 hopes.”

While Democrats are pushing a story line that hinges on the House Republican plan to fundamentally reshape Medicare, polling suggests that tightening of the race more likely reflects the presence of Davis, who is on pace to spend $3 million before the election and is draining significant support from Corwin. Republican strategists said tearing down Davis may be the best formula for holding the seat left vacant by the resignation of Rep. Chris Lee (R).

“This race has become artificially competitive because liberal Democrat Jack Davis is now trying to pass himself off as a conservative while the other liberal Democrat, Katie Hochul, is benefiting from his trick,” American Crossroads spokesman Jonathan Collegio said. “This ad buy seeks to expose the Democrat trick for what it is.”

But high-profile Democrats will head to western New York in the coming weeks to help their nominee. Sen. Charles Schumer is set to visit this weekend, with a separate visit by Sen. Kirsten Gillibrand planned for the next.

The visits come in the wake of appearances there by Speaker John Boehner (R-Ohio) and House Majority Leader Eric Cantor (R-Va.), who was asked Tuesday whether the Republican Medicare plan was hurting their candidate.

“It’s job creation, it’s free markets, it’s innovation, and she’s taken that message to the voters and I believe will be successful,” he said.

On the other side, House Minority Whip Steny Hoyer downplayed expectations but sounded somewhat optimistic.

“It’s a heavily Republican district. Our expectations there are very, very difficult,” the Maryland Democrat said. “But we have a quality candidate, and the answer to your question is I think should we win that election.”

Jessica Brady contributed to this report.

Editor’s Note:

The online version of this article has been updated to confirm that American Crossroads is targeting Jack Davis in its advertisement released Tuesday night.