The House Majority Political Action Committee will unveil what it calls a television “advertising offensive” across western New York on Tuesday, a move that tests the fledgling organization’s ability to balance conservative outside groups in next week’s suddenly high-profile special election.

The Democratic ally attacks GOP nominee Jane Corwin for supporting a plan that “would essentially end Medicare” and “increases the debt by giving tax breaks to big oil and millionaires,” according to a copy of the ad obtained by Roll Call.

Known as a “super PAC,” House Majority was created in the wake of the 2010 midterm elections, when outside conservative groups such as American Crossroads — freed from traditional campaign limits following the Supreme Court’s Citizens United decision — diverted a river of money into key Congressional contests around the country. Crossroads has already committed $650,000 to next Tuesday’s contest.

While most of the conservative groups do not disclose their donors, House Majority accepts unlimited donations but reports the source of its funding. Tuesday’s buy, which will run on broadcast and cable television in New York’s 26th district through Election Day, is in the “low six figures,” according to a source with knowledge of the situation.

Democrats have been pushing the storyline that the special election is essentially a referendum on the House Republican budget plan, which fundamentally reshapes Medicare. But the tightening of the race likely has much more to do with the presence of a wealthy third-party candidate, Jack Davis, who is siphoning support away from Corwin, who had been expected to cruise to victory in a district that is among the most conservative in the Empire State.

Both Davis and Corwin, an independently wealthy state legislator, have spent more than $2 million from their own pocket to date. And outside groups such as House Majority have dumped hundreds of thousands more into television advertising, which has been blanketing the Buffalo and Rochester airwaves for much of the past month.

Labor unions also have people on the ground, as do the Tea Party Express and both the Democratic and Republican Congressional campaign committees. Volunteers from both sides are expected to flood to the area this weekend, in anticipation of the May 24 election.

Watch the ad: