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By the Numbers: GOP Edges Dem Groups in Senate Ad Spending

New data shows that campaigns, committees and outside groups combined have poured nearly $380 million into top Senate races.
Image: An employee of the Korea Exchange Bank counts one hundred U.S. dollar banknotes in Seoul
An employee of the Korea Exchange Bank counts one hundred U.S. dollar banknotes at the bank's headquarters in Seoul, August 11, 2011. U.S. stock futures rose 1.5 percent on Thursday after a sharp drop in the cash index overnight, limiting Asian share losses, though focus will shift quickly to how European markets hold up to a sovereign debt crisis that has spread to its banking system. REUTERS/Jo Yong-Hak (SOUTH KOREA - Tags: BUSINESS)JO YONG-HAK / Reuters

While Democrats might have more incumbents with fundraising firepower, Republicans have still outspent Democrats on the air in every top Senate battleground since the end of the primaries, new media buying data shows.

Data given to NBC News by GOP ad-buyer Smart Media shows that campaigns, committees and outside groups combined have poured a total of nearly $380 million into Senate races in Alaska, Arkansas, Colorado, Georgia, Iowa, Kansas, Kentucky, Louisiana, North Carolina and New Hampshire.

Republicans are winning the money race in all 10 of those states, with GOP-aligned groups funneling a total of about $208 million into the top races. Democratic groups have spent about $169 million in the same contests.

Democrats have kept the margins fairly narrow in most states. (The exception is the Arkansas contest between Tom Cotton and Mark Pryor, where Republican-backed groups have spent $24 million to Democrats’ $17 million.)

For example, in Alaska -- which has a voting-age population of about 550,000 – Republican groups have spent a total of $14.2 million since the primary. Democratic groups have spent about $11 million to boost incumbent Sen. Mark Begich there.

North Carolina wins the prize for the most spending overall, with both sides forking over $77 million for ads in the state. Republicans shelled out about $38.9 million for Tom Tillis, and Democrats are close behind at $38.4 million for Sen. Kay Hagan.

Republicans have also dumped $6.8 million on the unpredictable Senate contest in Kansas, where Sen. Pat Roberts is trying to fend off a challenge from independent Greg Orman. Orman and his backers have spent $2.3 million so far.

Part of the reason for the GOP advantage is the heavy influence from outside groups like those funded by the Koch brothers.

Four Koch-backed organizations – Americans for Prosperity, Freedom Partners, Generation Opportunity and Concerned Veterans for America – have spent an eye-popping $33 million on top Senate contests since the end of each state’s primary elections. That includes about $7 million in both Iowa and Louisiana and $5 million in both Arkansas and North Carolina.

For Democrats, one major contributor is environmentalist billionaire Tom Steyer, who has pumped $5.6 million into races in three states: Colorado, Iowa and New Hampshire. But Koch-backed organizations spent almost that sum in the Arkansas Senate race alone.