The Service Employees International Union (SEIU) has spent about $90,000 on mailers for New York special election candidate Scott Murphy.
The independent expenditure was filed with the Federal Election Commission (FEC) on Wednesday.
So far, the Democratic Congressional Campaign Committee (DCCC) has spent about $150,000 helping Murphy, while the National Republican Congressional Committee (NRCC) has spent nearly $200,000 supporting Tedisco.
The special election for appointed Sen. Kirsten Gillibrand