“You’d think we could have more influence,” Charles Koch told the F.T. last month over pulled-pork sandwiches at the staff commissary of Koch Industries in Wichita, Kansas. The wealthy industrialist and conservative impresario was giving a rare interview in support of his new book, but his disillusionment with the state of the Republican presidential race (and politics in general) was apparent. In 2012, he and his younger brother, David Koch, raised approximately $400 million through their donor network with the primary goal of electing Mitt Romney—only to be outmaneuvered in the end by Barack Obama’s campaign. During the intervening years, the Kochs’ political operatives studied what had gone wrong in 2012 and redoubled their efforts to ensure that the same fate would not befall them again. By the start of the 2016 election cycle, the brothers and their allies had pledged to raise nearly $900 million to elect Republicans, particularly whomever ends up facing Hillary Clinton—or, perhaps, Bernie Sanders—in the general election.

But things don't seem to be working out as smoothly as planned. Like other members of the Republican elite, the Koch brothers misjudged Donald Trump. They never considered the real estate scion a serious contender, and his politics on taxes, trade, and foreign policy clashed thoroughly with theirs. (Charles Koch noted that Trump’s Muslim registry, for instance, would “destroy our free society.”) Even when Trump, who has known David for years, sought their support—going as far as hiring Corey Lewandowski, a veteran of their advocacy group, Americans for Prosperity, as his campaign manager—the Kochs rebuffed him. Then Trump turned on them. When the Koch network left Trump off the invite list for an August donor summit attended by five of his G.O.P. rivals, he trolled his opponents on Twitter: “I wish good luck to all of the Republican candidates that traveled to California to beg for money etc. from the Koch Brothers. Puppets?”

Charles Koch’s candid lament at the office canteen drew predictable ridicule from critics on the left, who found it deliciously ironic coming from a billionaire marshaling hundreds of millions of dollars to sway the election. But the comment also revealed a different irony: the Kochs, after building a shadow party on the right, are now struggling to gain traction in a political landscape they have helped to bring into existence.

This election cycle was supposed to be the one in which the Koch network­ fulfilled its mission of installing a Republican in the White House. But that goal, and the millions behind it, are at risk. And before the Kochs begin to take on Hillary or Bernie, they are carefully considering whether to wage a war against Trump.

The Kochs had initially opted against engaging in the primaries, both because there was no consensus pick within their network or a single candidate who encapsulated their views. (The closest one, ideologically, was Rand Paul, who dropped out of the race on Wednesday.) But for months, the Koch network has considered diverting a portion of its massive war chest to a campaign targeting Trump, even at the risk of alienating a handful of their members who support the candidate. Koch officials say they will move forward with this plan based on how the early primaries shake out. (Ted Cruz’s caucus win on Monday must have come as a mild relief.)

But Trump’s second-place Iowa finish was more a blow to his ego, in some respect, than the viability of his campaign. If he prevails in New Hampshire, where he’s maintaining a huge lead in the polls, pressure is likely to mount within the Koch network to launch an offensive before a march to the nomination gains formidable momentum. When the Kochs and several hundred of their allies gathered last weekend for another summit, halting Trump was a major topic of discussion.