by Joan McCarter

David Koch, executive vice president of Koch Industries, attends an Economic Club of New York event in New YorkSince September, Americans for Prosperity, a group financed in part by the billionaire Koch brothers, has spent an estimated $20 million on television advertising that calls out House and Senate Democrats by name for their support of the Affordable Care Act.

The unusually aggressive early run of television ads, which has been supplemented by other conservative initiatives, has gone largely unanswered, and strategists in both parties agree it is taking a toll on its targets. […]

Some House Democrats in competitive districts find themselves under steady assault with little ability to respond unless they want to dip into money they will need later in the campaign.

“Money spent now is money lost,” said Representative Joe Garcia, a South Florida Democrat who was the target of an ad campaign late last year along with Representative Patrick Murphy, a fellow Floridian. Both are in their first terms, and freshmen incumbents are usually considered the most vulnerable.