American Crossroads, a conservative-aligned outside group, is launching television ads this week in the special election for New York’s 26th district, the latest sign that the race has tightened considerably.

American Crossroads will spent roughly $350,000 this week on broadcast and cable in the Buffalo and Rochester media markets. A second week of ads is already planned with Democratic ad buyers estimating the total Crossroads expenditure to be in the neighborhood of $650,000.

While the ad itself is not yet available, Crossroads spokesman Jonathan Collegio said that “this race has become artificially close 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.” Added Collegio: “This ad buy seeks to expose the Democrat trick for what it is.”

The race for former Rep. Chris Le e’s (R) Upstate seat was not expected to be close. Arizona Sen. John McCain (R) carried the district by six points in 2008 and national Democratic strategists initially downplayed its competitiveness.

But, the decision by Davis, a well-heeled political gadfly who ran for the seat as a Democrat in 2006 and 2008, to enter the race as an independent aligned with the tea party has re-oriented the winning equation for both parties.

Davis has already loaned his campaign more than $2 million and polling suggests that his rise has complicated what should have been a relatively pedestrian victory by state Assemblywoman Jane Corwin (R). (Corwin has gone on the attack against Davis by noting his Democratic past in an ad.)

That splitting of the Republican vote has allowed Hochul a viable path to victory just two weeks out from the May 24 special election.

National Democrats have yet to invest in television ads in support of Hochul’s candidacy, but they have spent upwards of $50,000 in coordinated funds on the race and have raised a similar amount into her campaign.

It’s not clear whether the Crossroads buy and the perceived closeness of the special election will entice the Democratic Congressional Campaign Committee to buy air time of its own in the district.

“American Crossroads’ desperate ad buy for Jane Corwin shows ... the issues are effectively moving the needle in what should be safe Republican seat,” said Josh Schwerin, a DCCC spokesman in a statement after the acnnouncement.

The House Majority PAC, a Democratic-affiliated group formed earlier this year to raise and spend money in House races, said only that it is ”keeping very close tabs” on the contest.