Indiana Gov. Mike Pence introduces Republican presidential candidate Donald Trump at the Grand Park Events Center on Tuesday in Westfield, Ind. (Aaron P. Bernstein/Getty Images)

Indiana Gov. Mike Pence has been a favorite of the Koch political operation and a featured speaker at Koch-backed events. But that doesn't mean his selection to be Donald Trump's running mate would mobilize the network of conservative nonprofit groups in support of the Republican presidential ticket.

"It doesn't change our engagement on the presidential," James Davis, a spokesman for Freedom Partners, the network's funding arm, said on Thursday. "We are going to remain focused on the Senate."

The network's unwillingness to activate its ground operation and advertising resources to back Trump has exasperated some top Republican donors and highlighted the deep rift between the billionaire real-estate developer and some of the most influential figures in the conservative movement. The firm stance is driven by billionaire Koch Industries chief executive Charles Koch, who has repeatedly expressed his dismay with Trump's tone and policy positions.

A meeting last month between Koch Industries general counsel Mark Holden and Trump campaign officials did not appear to change the dynamic. In an interview Monday at Fortune’s Brainstorm Tech conference, Charles Koch compared the choice of Trump and Democratic contender Hillary Clinton as having to vote "for cancer or heart attack."

"I’m sure he’s a fine fellow underneath, but when you look at our guiding principles, you see that his guiding principles are in many ways antithetical to them and a great many of his policies are antithetical," the industrialist said of Trump.

The network's posture takes a major piece of the political infrastructure on the right out of the equation, at least when it comes to the presidential race. After originally planning to spend $889 million in the 2016 cycle, the Koch operation is now on track to spend $750 million, with roughly a third — $250 million — financing the policy and political campaigns of groups such as Americans for Prosperity, Freedom Partners Action Fund, Concerned Veterans for America, the LIBRE Initiative and Generation Opportunity, officials said.

The network's efforts could still indirectly boost Trump, as we reported last month. The Koch operation’s field teams are gathering reams of information on voters in key battleground states, intelligence that filters back to the Republican National Committee and GOP candidates through a data-sharing agreement. And its robust ground force, which far outstrips Trump’s meager field operation, could help prod ambivalent voters to the polls in key swing states.

Last month, AFP launched ground operations on behalf of GOP incumbents in Pennsylvania, Ohio and Wisconsin — the earliest the group has ever begun making explicit political appeals in the field.