These activists have been sprinting through Pennsylvania neighborhoods, talking to people about how bad Democrat Katie McGinty would be as a U.S. senator. Here to help save Republican Sen. Pat Toomey — and, more broadly, the party’s control of the Senate — are employees and volunteers for Americans for Prosperity, the best-known group financed by conservative billionaires Charles and David Koch.

Similar scenes are playing out in North Carolina, Florida and Ohio.

In addition to having nail-biting Senate races this year, those four states are some of the most important battlegrounds in the presidential race. Yet the Koch activists interacting with millions of people who could be Trump’s most crucial voters aren’t supposed to utter a word about him or Hillary Clinton, a Democrat they’d been preparing for years to attack.

Four years after spending heavily in a futile effort to prevent President Barack Obama’s second term, the Kochs have pushed all of their resources down ballot. And their resources are ample: They’re on track to spend about $250 million on policy and politics in the two years leading to Election Day.

The brothers and many of their wealthy donor friends who fund the political and policy groups known as the Koch network have no interest in backing Trump. In a television interview in April, Charles Koch called Clinton and Trump “terrible role models” and trashed Trump’s “monstrous” proposal for a temporary ban of foreign Muslims entering the U.S.

Koch Network Refusing to Help Trump

In the months since, while many Republicans flipped back and forth as to whether to support their nominee, the Kochs never considered engaging in a Trump-Clinton match, even when some donors pressed them at a conference in August.

Instead, Koch groups have spent about $42 million on TV, radio and digital advertising in Senate races. As of this month, they have abandoned paid media altogether, preserving their money for what is a much more critical hole to plug: door-to-door advocacy.

Trump’s campaign has eschewed traditional political grunt work, leaving that to overworked national and state Republican parties, which must advocate for GOP candidates from Trump down to the local council members.

Outside groups led by a former chief of staff to Senate Majority Leader Mitch McConnell, R-Ky., continue to spend on ads—they’ll hit about $100 million by Election Day. But the Senate GOP campaigns could really use help on the ground, and that’s where the Koch network comes in. Americans for Prosperity and other groups employ more than 1,200 across 36 states.

To operate as effectively as possible, the Kochs’ data analytics shop, called i360, identified what it believes are 5 million Senate control-deciding voters in eight states. Those voters are either Republicans who seem unenthusiastic this year, perhaps turned off by the ugliness of presidential race, or people who hadn’t quite made up their minds about the Senate contest but lean Republican.

Roughly 600,000 of those key voters are in Pennsylvania.

Trump’s Pennsylvania Supporters Grapple with New Accusations

During a recent weekend push in Bucks County, one of the most politically contested areas of the country, Americans for Prosperity temporarily imported employees from New Jersey and New Hampshire. There’s no Senate race in New Jersey, and the Kochs aren’t assisting Sen. Kelly Ayotte, R-N.H., largely because she sided with the Obama administration’s moves to cut carbon emissions; that’s at odds with the Kochs’ push for fewer regulations.

At a hotel conference room one Thursday evening, Pennsylvania AFP field director Jeremy Baker prepped the out-of-state helpers for the no-nonsense attitude of many southeastern Pennsylvanians: “Well, they don’t want you to knock on their door at all, but when you do knock on the door, you want to be concise. You’re not going to have a 30-minute conversation with these folks. That being said, this is an area where we can have a lot of impact on this election.”

Part of the team had been out that afternoon, shoving their electronic tablets into Ziploc bags to protect them from a steady rainfall. They’re averaging about 11,000 door-knocks per week across the state. Very little stops them from going out every day.

“We’re asking people to vote against Katie McGinty,” Ed Saterstad, a 37-year-old part-time AFP employee, said to the man who’d answered the door, Bob Ryan.

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Saterstad began a short survey portraying McGinty as liberal and bad for Pennsylvania, asserting, for example, that her energy policies would raise prices. Saterstad chronicled Ryan’s responses on his tablet.

Less than a minute later, Saterstad concluded, “After hearing all this about Katie McGinty, does that make you more likely or less likely to support her?” Ryan chuckled. “I wasn’t going to support her anyway, but, less.”

Ryan later told a reporter no one had yet knocked on his door to talk about the presidential race. It’s just as well. Asked for his thoughts on it, he sighed heavily.

“I just can’t believe it’s the best we can do,” said the Republican-turned-independent. “I think Trump’s a disaster, and I think Clinton is a pure political opportunist. I’m aghast that that’s the best we can do, let’s put it that way.”

He wasn’t sure if he’d cast a vote for president. But if he does vote, he said, it’ll be for Toomey.