Koch advisor joins Marco Rubio. Will Koch brothers' money follow?

A top Koch brothers advisor will be joining Team Rubio, the Florida Senator's campaign has confirmed, suggesting the business moguls and political-donor heavyweights may be inching closer to an endorsement.

Marc Short has resigned from his position as president of Freedom Partners, a Koch-funded nonprofit that promotes "the benefits of free markets and a free society," and will sign on as a senior advisor to Sen. Marco Rubio, Politico reported on Tuesday. Rubio's campaign confirmed the news Wednesday.

"This is a big get for Rubio," Phil Cox, a former executive director of the Republican Governors Association, told Politico. "Marc brings a unique perspective as one of the few people who have had one foot in traditional Republican Party politics and another in more movement-conservative efforts."

Since Donald Trump's second primary win, in South Carolina, establishment Republicans, governors, senators, and donors have been flocking to Senator Rubio as "anyone but Trump" warnings grow more dire. Potential help from Charles and David Koch, and the massive political machine they coordinate, can give a decisive financial boost to candidates in a typical year. In the next two years, their various organizations will spend $750 million, including $250 million in campaign money, Charles Koch told American Public Media.

But it's not a typical Republican primary season, and not only because of Trump's questionable conservative bona fides. His wealth, and penchant for personal attacks, has scared off many of the party's usual big-pocket supporters.

Mega-donors like the Kochs, or casino magnate Sheldon Adelson, are typically fought-over endorsers for Republican candidates. But not only does Trump have a massive bank account of his own, but he's turned the rules of campaign funding on their head, relying more on outrage-driven free media coverage than expensive ad campaigns.

Many spenders are wary of dedicating too much money during the primaries, in hopes of saving it for a general election blitz. The libertarian-leaning Kochs themselves have not endorsed any 2016 candidates, although Charles Koch's Feb. 18 op-ed in The Washington Post outlined the qualities he'd like to see in one, along with agreement with his own small-government, pro-free trade views:

All Americans deserve a president who, on balance, can demonstrate a commitment to a set of ideas and values that will lead to peace, civility and well-being rather than conflict, contempt and division. When such a candidate emerges, he or she will have my enthusiastic support.

But Trump, whose business, tax and trade views run counter to the Kochs' own, may have pushed their patience to the edge. Donors at the brothers' biannual retreat, held in late January, debated strategies to highlight his weaknesses, anxious to stop not only his economic policies but his "Caesar-like" vision of leadership, as the Hill reported.

"Support for Trump is not philosophical," Mr. Short, Rubio's new advisor, said at the time. "It's a frustration and even an understandable anger that people feel, that their representatives in Washington don't represent their interests anymore," he told Bloomberg. "We agree with the frustration, but we just feel like that's the wrong prescription to solve the problem."

But a willingness to attack Trump is still scant, would-be donors say. Some would like to run negative ads, but are scared off by the prospect of lawsuits or threats.

Others fear that big-money attacks will only fuel perception of Trump as a political "outsider," a main pillar of his appeal.

"There are a lot of donors who would like to do more, but they are going to have to regroup and find out what message works. Every time you go against him, it just makes him stronger," Frayda Levin, a board member of the Club for Growth, which Trump threatened with legal action after it ran negative ads, told Politico. "We're running against the clock."