A Democratic super PAC is looking to counter the Koch brothers’ big-money influence in battleground states as the 2014 midterm election cycle heats up.

The Senate Majority PAC, a group that supports Democrats up for re-election, is set to spend $3 million on ads in Arkansas, Colorado, Louisiana, Michigan, and North Carolina, nearly doubling what they’ve spent so far this cycle, according to the New York Times.

Americans for Prosperity (AFP), the group backed by conservative billionaire brothers Charles and David Koch, has already spent 10 times that on TV ads in midterm races, according to the Times, going after vulnerable Democrats. The Koch brothers were among the biggest spenders in the 2012 election, when AFP spent $122 million, most of it aimed at unseating President Obama.

Senate Majority PAC plans to spend $500,000 in Arkansas, Colorado, Louisiana and Michigan. The group is set to spend $1 million in North Carolina to defend Democratic Sen. Kay Hagan, who faces a tough re-election fight, the Times’ report said.

An ad running in Colorado, released online Thursday, asks voters to “take a closer look” at the anti-Obamacare ads from AFP targeting Democratic Sen. Mark Udall. “Who’s behind those attacks? Insurance companies and out of state billionaires,” the narrator says.