Bernie Sanders has been outspending rival Hillary Clinton on ads just as the Democratic presidential race appears to be tightening and voters are tuning in.
In the past three weeks, Sanders' campaign has spent $4.7 million on ads to Clinton's $3.7 million. According to advertising tracker Kantar Media's CMAG, that means 1,000 more Sanders commercials than Clinton ads on broadcast TV.
The Sanders ad burst is coinciding with his rise in preference polls in Iowa and New Hampshire.
Clinton began advertising three months before Sanders, in August. The CMAG numbers show that over the entire contest she's outspent him by about $3 million.
But lately he's outpaced her with ads as he's posted gains in surveys in the first states to vote. Iowa votes Feb. 1; New Hampshire, Feb. 9.