The well-funded conservative group American Crossroads has reserved $650,000 in television advertising time in New York’s 26th district, becoming the first outside group to devote significant resources to a special election that has become far closer than it was supposed to be.

The television reserve, which includes broadcast in the Rochester and Buffalo markets, will begin Tuesday and run through the day of the election, May 24, according to Democrats tracking media reserves.

Both the National Republican Congressional Committee and the Democratic Congressional Campaign Committee have been reluctant to invest substantial resources in the conservative district, but Crossroads’ move could open the floodgates in a three-way contest that has already seen massive personal investments by the Republican nominee, Jane Corwin, and third-party candidate Jack Davis, a former Democrat who will appear on the “Tea Party” ballot line.

A poll done by a Democratic firm and released this week showed Democratic nominee Kathy Hochul with a 4-point lead over Corwin, who was largely expected to cruise to victory in a district that is among the state’s most conservative.

Speaker John Boehner (R-Ohio) stumped in the district on Monday for Corwin.