Both sides should probably brace themselves for modest results.
Turning behind-the-scenes players into central figures is difficult when so many Americans have no idea who these people are. A March GWU Battleground poll showed that 52 percent of Americans didn't know who the Koch brothers were and another 11 percent had no opinion of them. In an April NBC News/Wall Street Journal poll, nearly half the county (49 percent) didn't know the Kochs and another 20 percent were neutral toward them.
Democrats have amped up their anti-Koch rhetoric in the months since those polls were conducted -- in Senate floor speeches, ads, interviews and campaign talking points. But as those underwhelming numbers show, they had their work cut out for them. Turning the billionaire industrialist brothers -- who fund conservative candidates and causes through groups like American For Prosperity -- into figures loathed enough by Democratic voters to boost turnout was always going to be a big challenge.
When it comes to Steyer, the task may be even more daunting. He's a newer arrival on the national stage. This is the first election cycle in which Republicans have really tried to pillory him. There is no public polling on Steyer, but it would defy logic to believe that he is much better known than the Kochs.
Steyer is targeting races with his deep pockets through his super PAC, NextGen Climate Action Committee, which is what has stirred Republicans. The conservative super PAC American Crossroads and its affiliated nonprofit Crossroads GPS has already launched at least two anti-Steyer TV ads in Senate contests in Iowa and Michigan, races where NextGen has spent money.
Picking on Steyer and the Kochs does make it easier for candidates and super PACs to raise money, since it gives them villains for fundraising e-mails. At the margins, it's possible the negative campaigns may turn out hard-core base voters concerned about money in politics or climate change. And the attacks are not going unnoticed by the targets: Koch Industries has launched positive ads to counter Democratic broadsides.
On the whole, though, there simply isn't much evidence to suggest that any of this will influence voters' thinking significantly enough to affect any outcomes this fall. Polling shows the state of economy is still at or near the forefront of voters' minds. Foreign policy and national security has reemerged as a major topic of debate, amid the backdrop of the U.S. airstrikes against the Islamic State in the Middle East. Campaign finance is not a central focus.
Steyer and the Kochs are taking a lot of heat right now. But come Nov. 4, it may end up meaning very little.