A leading Democratic super PAC released a pair of TV ads Wednesday that aim to tie GOP Senate contenders in North Carolina and Louisiana to Charles and David Koch, billionaire industrialist brothers who back a group that has been spending big against vulnerable Democratic senators. It's the latest part of on ongoing national Democratic push to make the Koch brothers into campaign bogeymen this year.

Here's the ad targeting Republican state House Speaker Thom Tillis in North Carolina:

And here's the spot that goes after Rep. Bill Cassidy (R-La.):

The ads are part of Senate Majority PAC's new $3 million campaign in a handful of states meant as a countermeasure against the ad blitz from Americans For Prosperity, a conservative group backed by the Koch brothers that has spent big against Sens. Mary Landrieu (D-La.) and Kay Hagan (D-N.C.), among others.

Democrats are making a big push to try to make the Koch brothers into a campaign issue. But a poll released Tuesday showed half the public doesn't know who they are.