The National Republican Senatorial Committee has launched an independent expenditure ad charging Sen. Mark PryorMark PryorCotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm Top Democrats are no advocates for DC statehood MORE (D-Ark.) “voted to give Social Security benefits to illegal immigrants.”

The 30-second spot, a copy of which was obtained by The Hill, shows a desk lamp illuminating a file folder and corkboard filled with details on GOP charges against Pryor.

“What's Mark Pryor hiding? Let's take a look,” a narrator says.

The ad charges the senator “voted to give members of Congress special benefits to purchase Obamacare, and despite record spending and trillions in new debt, Pryor voted against a balanced budget amendment.”

It concludes: “Mark Pryor: Shine a light on his record and things don't look so good.”

The ad is part of the more than $1.9 million in advertising on radio and television between now and Election Day in Arkansas.

Records indicate the ad launched Tuesday, the same day the Democratic Senatorial Campaign Committee went on air with an ad charging Pryor’s GOP opponent, Rep. Tom CottonTom CottonKoch-backed group stepping up advocacy against border tax GOP senator: 'Serious concerns' about House border tax plan GOP senators to Trump: We support 'maintaining and expanding' Gitmo MORE, misled voters on his support for funding for a local children's’ hospital.

The attack joins another launched Tuesday by GOP group Crossroads GPS that hammers Pryor on Medicare cuts.

It's the latest salvo in a fierce air war that's only expected to get more aggressive as the Arkansas Senate race, a key pickup opportunity for the GOP in its pursuit of the Senate majority, heats up.