The National Republican Congressional Committee is reserving nearly a half-million dollars in cable television airtime to support Rep. Joe Walsh (R-Ill.), the first time the committee has signaled it would spend on behalf of the embattled congressman.

The group's air reservation is set to begin Oct. 5 and run through Election Day, a sign the committee might be growing more bullish about Walsh's chances against Democrat Tammy Duckworth in the Democratic-leaning suburban Chicago district.

While a half-million dollars is a major investment, in the expensive Chicago media market it won't reach saturation levels — and the committee has larger reservations in place for two other suburban Chicago Republicans, Reps. Judy Biggert (R-Ill.) and Robert Dold (R-Ill.).

Walsh had been one of a handful of Republican incumbents in tough races the committee had yet to invest in. Democrats are going through the same process, cutting back on ad reservations for Rep. Larry Kissell (D-N.C.). Ad reservations are fluid: The committee could add to the reservation or cancel it depending on whether it thinks the race is tightening. The Hill currently rates this race "likely Democratic."

The reservation was confirmed to The Hill by both Democratic and Republican ad trackers.