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 (Tim) Michael KaineSave lives, restore congressional respect by strengthening opioids’ seizure Overnight Finance: Lawmakers, Treasury look to close tax law loopholes | Trump says he backs gas tax hike | Markets rise despite higher inflation | Fannie Mae asks for .7B Bipartisan Senate group says they have immigration deal MORE (D) and former Sen. George Allen (R). In Missouri, Sen. Claire McCaskillClaire Conner McCaskillMcCaskill welcomes ninth grandson in a row Dem group launches M ad buy to boost vulnerable senators Senate Dems block crackdown on sanctuary cities MORE (D) is seen as a top GOP pickup opportunity. Montana Sen. Jon TesterJonathan (Jon) TesterWith vote against Brownback, Democrats abandon religious freedom Democrat Manchin: Pence attacks prove ‘they don't want bipartisanship’ in Trump admin Tester invited the Border Patrol Union’s president to the State of the Union. What does that say to Dreamers?   MORE (D) is also seen as vulnerable. In Nevada, Republicans are defending newly appointed Sen. Dean HellerDean Arthur HellerThe siren of Baton Rouge Big Republican missteps needed for Democrats to win in November What to watch for in the Senate immigration votes 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 BaldwinAmerican women will decide who wins and loses in 2018 elections Grassley, Dems step up battle over judicial nominees 10 Senate Democrats are up for reelection in Trump country 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 WarrenTrump's SEC may negate investors' ability to fight securities fraud Schatz's ignorance of our Anglo-American legal heritage illustrates problem with government Dems ponder gender politics of 2020 nominee 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.