House Republicans have doubled their investment in the special election to replace former Rep. Gabrielle Giffords (D-Ariz.).

The National Republican Congressional Committee (NRCC) is upping the $300,000 they've already spent on the air in Arizona to $600,000, a source with knowledge of the decision told The Hill. The NRCC's ads target Ron BarberRonald (Ron) Sylvester BarberKavanaugh nomination a make or break moment to repeal Citizens United Latina Leaders to Watch 2018 Principles and actions mean more than Jeff Flake’s words MORE, a former Giffords staffer and the Democratic nominee to finish her term.

The Democratic Congressional Campaign Committee (DCCC) is also on the air, with $473,000 in airtime reserved. The DCCC's ads run through Thursday, then go dark for about three weeks before picking up again in early June — two weeks before the special election.

In the three weeks during which the DCCC will be dark, House Majority PAC, a Democratic super-PAC, will spend $340,000 on ads targeting Jesse Kelly, the Republican nominee.

The air wars have become a game of poker between the Democratic and Republican campaign committees. When the NRCC announced in April it would drop $150,000 on the race, the DCCC responded hours later with its own buy for the same amount. Republicans increased their buy a few days later to $300,000, prompting Democrats to up their independent expenditures to almost $500,000.

Both parties are eager to control the seat that Giffords held for three terms until she resigned in January, one year after being critically wounded in a shooting spree in her district that also injured Barber.

The Tucson, Ariz.-based district is competitive for both parties, but will become slightly more Democratic when new lines kick in after the special election. A second, regular election for the full term starting in 2013 will be conducted in the fall. Both Kelly and Barber have indicated their interest in a full term.