"It is surprisingly easy to get outside groups to collectively spend hundreds of millions of dollars and go very negative on your behalf. But they are not doing it simply because they like you. They must be convinced that you have a real shot at winning the election."

In 2012, Barack Obama and Mitt Romney spent almost $1 billion dollars each. However, that figure was matched by outside spending, none of which had to support campaign staff and try to push for the expensive ground game payments to boost turnout.

The outside players have an ability to focus their spending in a way that a candidate cannot. The result is that outside money may be more important than money raised by the candidate or the party.

Trump may have been able to sweep up huge amounts of donations from his fervent supporters, but he does not seem to have motivated the big outside actors. With the exception of one hedge fund friend, as well as the National Rifle Association, there has not been a significant pro-Trump effort from super PACs and others.

There have been two super PACs supporting Trump that have been in the news, one, Rebuilding America Now, has reportedly spent $6.3 million, and the other, Great America PAC, has put down $7.5 million. This may sound like a lot of money, but it is not in the context of a presidential campaign.

In contrast, the primary pro-Clinton super PAC, Priorities USA Action, reportedly raised over $100 million and has spent almost $40 million so far. The Priorities USA ads have been among the most noteworthy – and negative – advertising of the campaign.

As past elections have shown, it is surprisingly easy to get outside groups to collectively spend hundreds of millions of dollars and go very negative on your behalf. But they are not doing it simply because they like you. They must be convinced that you have a real shot at winning the election. Otherwise, they are just upsetting the next president. Trump's economic advisory board is made up of several such men who can take this tack. But as of yet they have not spent on him in a serious way.

It could be that he has looked for the wrong types of plutocrats. Or it could be that they don't believe he will win and therefore have been hesitant in opening up their wallets and angering the next president.

Trump, who had been happy to wage a throwback campaign focused on free media and one-shot campaign events, may not see this as a problem. But now his strategy is going to be tested, and despite his claims of wealth, his biggest weakness may be not having enough rich friends in his corner.

Commentary by Joshua Spivak, a senior fellow at the Hugh L. Carey Institute for Government Reform at Wagner College in New York. He blogs at The Recall Elections Blog. Follow him on Twitter @recallelections.

For more insight from CNBC contributors, follow @CNBCopinion on Twitter.

