The Obama campaign and the DNC have started to launch high profile attacks against the billionaire Koch Brothers in new advertising that links them to Mitt Romney. Matthew Zeitlin at the Washington Monthly wonders why they are focusing their attacks on the Kochs. He points out that it might be due to the unpopularity of Obama's actual legislative work:

Because two of Obama’s signature policy initiatives — the stimulus and health care reform — are not particularly popular, he is forced to run for reelection in light of the fact that the American public has broadly lost faith in the government’s ability to do anything right, but not make it seem like he is to blame for it. And how to do that? Relentlessly depict the Republicans, and the Republican nominee, as a puppet for the very forces who are truly responsible for cynicism about government....

Although aggressively championing actual campaign finance proposals will likely be awkward in light of Obama’s embrace of pro-Obama Super PACs, it is much easier to go after the GOP’s wealthiest supporters. The fact that the GOP primary is as much a fight between Super PAC donors as it is candidates makes this line of attack even more plausible.

If it’s going to be hard to convince the public your accomplishments are significant and that your policy proposals are good ones, your second best option might be to convince voters that the other guys aren’t even trying to do something good in the first place.

Which begs the question: if the President's signature pieces of legislation are not popular, why are Republicans unable to capitalize on that and do better in polling among independents and other voters? (The answer might be that they have spent the last month discussing contraception.)