House Republicans are preparing to unleash $722,000 in political advertising to support U.S. Rep. Bobby Schilling's election campaign.

The independent expenditure arm of the National Republican Congressional Committee has reserved $18 million of ad space across 25 congressional districts, including the $722,000 in the Quad Cities market, according to an NRCC source.

Rep. Schilling, R-Colona, is being challenged in the November election by Democrat Cheri Bustos, a former East Moline alderwoman.

The Democratic Congressional Campaign Committee already has reserved $1 million in advertising in the Quad Cities and Cedar Rapids markets, which covers Rep. Schilling's 17th District and the Iowa 2nd District, where U.S. Rep. Dave Loebsack, D-Mount Vernon, is being challenged by Republican John Archer.

Reserving ad space ensures they won't be crowded out as election season draws closer in a presidential election season likely to be flooded with advertising from super PACs, although it also leaves flexibility to move money around later.

Formed in the wake of the Citizens United Supreme Court ruling in 2010, super PACs are political action committees that can take unlimited donations from individuals, corporations and unions, and use the money to support or oppose a candidate. Super PACs are not supposed to coordinate their ad campaigns with the candidate they support.

Democrats are confident of winning the 17th District. Republicans are fighting to hold on to a seat in a Democrat-leaning district that they won in 2010 for the first time since 1983.