House Democrats have purchased a total of $473,000 in ad time for the June 12 special election for Arizona’s 8th district, a committee official confirmed to Roll Call today.

That sum includes a previous $150,000 buy from the Democratic Congressional Campaign Committee for advertisements running through May 10. The new ad reservation targets airtime for the final two weeks of the race.

The large purchase is a symbol of just how competitive the race for the seat of retiring Rep. Gabrielle Giffords (D) has become. The DCCC’s reservation marks the largest buy from a candidate or campaign so far in the race.

Earlier this week, the National Republican Congressional Committee confirmed it had put down $300,000 in advertisements on behalf of the GOP nominee, veteran Jesse Kelly.

Former Giffords staffer Ron Barber is the Democratic nominee.

Roll Call rates this race as a Tossup.