The National Republican Senatorial Committee has reserved $25 million in television ad space for the fall election, an NRSC official tells The Hill, a major early investment for the committee.

It's almost unheard of for campaign committees to begin reserving ad time this early in the cycle, and the buy is a sign of how much super-PACs could affect this election. The combination of heavy super-PAC spending and the high-dollar presidential race means airtime in many of these states will get much more expensive in upcoming months. Some states could run out of available airtime long before the election, something that happened near the end of the 2008 campaign.

The buy is spread over six top targeted states: $5.5 million in Virginia, $5 million apiece in Missouri and Wisconsin, $3.5 million in Montana and $3 million apiece in Nevada and New Mexico. Most of those states are expected to be in play at the presidential level or have already seen heavy outside-group spending, making airtime purchase a prerogative.

Virginia has a competitive match-up between former Gov. Tim KaineTimothy Michael KaineDemocrats turn on Al Franken Avalanche of Democratic senators say Franken should resign Senate panel moves forward with bill to roll back Dodd-Frank MORE (D) and former Sen. George Allen (R). In Missouri, Sen. Claire McCaskillClaire Conner McCaskillDemocrats turn on Al Franken Trump rips Dems a day ahead of key White House meeting The Hill's 12:30 Report MORE (D) is seen as a top GOP pickup opportunity. Montana Sen. Jon TesterJonathan (Jon) TesterGOP and Dems bitterly divided by immigration Senate panel moves forward with bill to roll back Dodd-Frank GOP defeats Schumer bid to delay tax vote MORE (D) is also seen as vulnerable. In Nevada, Republicans are defending newly appointed Sen. Dean HellerDean Arthur HellerDems look to use Moore against GOP Senate hearing shows Fed chair nominee acts the part Senate GOP votes to begin debate on tax bill MORE (R) against Rep. Shelley Berkley (D). Wisconsin and New Mexico have open seats.

The stand-out on the list is Wisconsin, where Republicans have argued for months that they feel any of their candidates could give a serious challenge to Rep. Tammy BaldwinTammy Suzanne BaldwinDemocrats turn on Al Franken The Hill's 12:30 Report Avalanche of Democratic senators say Franken should resign MORE (D-Wis.) in the open seat, despite the polls and many pundits giving Baldwin an edge over the other Republicans in the field. This buy indicates the committee is putting its money where its mouth is.

Potentially competitive states missing from the list including North Dakota, Nebraska, Michigan, Ohio and Florida, states where one party or the other seems to have the edge right now, as well as Massachusetts, where an agreement between Sen. Scott Brown (R-Mass.) and Democrat Elizabeth WarrenElizabeth Ann WarrenOvernight Regulation: Net neutrality supporters predict tough court battle | Watchdog to investigate EPA chief's meeting with industry group | Ex-Volkswagen exec gets 7 years for emissions cheating Overnight Tech: Net neutrality supporters predict tough court fight | Warren backs bid to block AT&T, Time Warner merger | NC county refuses to pay ransom to hackers Avalanche of Democratic senators say Franken should resign MORE bars the committees from spending in the state.

Hawaii is also not on the list, although former Hawaii Gov. Linda Lingle (R) is known as a fundraising powerhouse and might not need the committee's help.

The NRSC official emphasized that this is the first of many buys, and other states could be added to the list.

The buy was first reported by Roll Call.