The political network led by billionaire industrialist Charles Koch is planning to spend millions supporting GOP Senate candidates this cycle. (Photo by Patrick T. Fallon for The Washington Post)

The political network backed by billionaire industrialists Charles and David Koch is set to invest more than $42 million on ads in key Senate races through the end of September, part of a ground-to-air effort the organization is making in key states to help Republicans retain their majority.

The network's latest foray: a $2.2 million television and digital campaign in Ohio targeting former governor Ted Strickland, who is running GOP incumbent Sen. Rob Portman. The spot by Freedom Partners Action Fund, the organization's super PAC arm, features an Ohio business owner who calls the state's job losses during Strickland's administration "devastating." It's the second such ad that Freedom Partners has run against Strickland.

In all, the network has spent $12.4 million on issue ads and political spots promoting GOP Senate candidates this cycle, the most of any independent group so far. Its affiliated organizations, which includes the conservative advocacy group Americans for Prosperity, are now reserving another $30 million in television and digital buys for August and September, according to a network official. The new campaigns will air in Nevada, Ohio, Pennsylvania and Wisconsin, with additional investment eventually planned for Florida.

The news of the network's expanded spending comes in the wake of a report in the National Review that the Kochs are retreating from the kind of intense national political activity they conducted during the last three election cycles. Late Monday night, officials pushed back against that notion.

"The network is and will continue to be fully engaged in 2016 political and policy battles," said James Davis, executive vice president for Freedom Partners Action Fund. "We’re look to maximize the number of freedom-oriented senators because they are good on a number of issues, particularly free speech."

It remains unclear if the organization will raise and spend the nearly $900 million it laid out as a goal at the beginning of the cycle. One big change since then: the network now appears unlikely to engage in the presidential race, as Charles Koch and other top network officials have expressed dismay with likely GOP nominee Donald Trump's tone and policies.

But Koch-backed groups are poised to play major roles in pivotal Senate contests, both on the airwaves and through their large field staffs. In all, the network has more than 1,200 permanent employees in 38 states, and the grassroots staffs of Americans for Prosperity, Concerned Veterans for America, the LIBRE Initiative and Generation Opportunity grew by 50 percent in 2015, according to a network official. Those ground forces have already contacted tens of millions of voters through phone calls and door-knocking, twice as many people than the network reached during the entire 2014 cycle.