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 KaineTim Kaine40 million fewer people expected to vote in 2018, study finds Al Gore warns Democrats about accusing Trump of treason Administration briefs Senate on progress against ISIS MORE (D) and former Sen. George Allen (R). In Missouri, Sen. Claire McCaskillClaire McCaskillFederal Election Commission must not shy away from Russia probe Senate Dems warn potential Missouri GOP recruit with opposition research dump GOP rep declines Senate bid challenging McCaskill MORE (D) is seen as a top GOP pickup opportunity. Montana Sen. Jon TesterJon TesterVulnerable senators raise big money ahead of 2018 'Kate's Law' battle shifts to the Senate, testing Dems Democrats go in for the kill on ObamaCare repeal MORE (D) is also seen as vulnerable. In Nevada, Republicans are defending newly appointed Sen. Dean HellerDean HellerPro-ObamaCare group targets key senators in new ads Overnight Healthcare: CBO predicts 22M would lose coverage under Senate ObamaCare replacement 40 million fewer people expected to vote in 2018, study finds 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 BaldwinSteel industry urges House panel to adopt 'Buy America' rules Major progressive group endorses Martha McSally challenger Vulnerable senators raise big money ahead of 2018 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 WarrenScaramucci deletes old tweets bashing Trump Trump's new communications chief once called him a 'hack' OPINION | Hey Dems, Russia won't define 2018, so why not fix your party's problems instead? 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.