Washington (CNN) - In the battle on the airwaves for the White House, it seems Republicans rather than Democrats are going negative more often.
Seventy percent of ads run by Democrats in the general election campaign for president have been positive in nature, while 73% of commercials run by Republicans were negative, according to data provided in a weekly note to their clients by Kantar Media/Campaign Media Analysis Group, which tracks political ad spending.
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Overall 51% of broadcast TV spots in the race for White House have been positive, while 49% have been negative, from April 10 through May 24. April 10 is the day former Sen. Rick Santorum of Pennsylvania suspended his presidential campaign. Santorum was former Massachusetts Gov. Mitt Romney's main rival for the Republican presidential nomination, and when he left the race, Romney became the presumptive GOP nominee.
The spots counted in the CMAG data include ads by the campaigns, party committees and independent groups.
The CMAG data also indicates that the Democrats have aired more ads than the Republicans. Fifty-six percent of commercials aired were from Democratic advertisers, mainly President Barack Obama's re-election campaign, while 44% were from Republican advertisers, mostly outside groups such as Crossroads GPS.
"The GOP groups are blocking and tackling for their nominee, letting Romney refill his campaign account post-primary and trying to keep the President from improving his standing in key areas. At some point, they may shift their focus more toward boosting Romney," CMAG Vice President Elizabeth Wilner told CNN.
The Obama re-election campaign is airing just over $25 million worth of commercials, mostly positive, in eight battleground states. Team Obama's ads went up May 9 and will run through next Monday.
Crossroads GPS, the conservative independent group co-founded by Karl Rove, is spending around the same amount of money in battleground states to run ads critical of the president.