Fortunately, most candidates have stated that they would try. That said, only Trump and Sanders aren't taking advantage of it by having affiliated super-PACs, the kinds that are ran and organized their allies. The PACs that support Trump and Sanders arose independently and are not under their control. Sanders even wants his supporting PACs to knock it off since it hurts his message of being only supported by the common people.
So there you have it, very similar positions by Trump and Sanders on universal healthcare, illegal immigration, H1B visas, free trade, Wall Street, and money in campaigns.
Now, this doesn't mean I like everything either man represents. Sanders' free education and $15 dollar minimum wage are nice sounding but quite possibly not economically feasible for the US.
For Trump, I certainly don't like a lot of his bloviating nonsense. His BS tweet about black people being responsible for 81% of the homicides of white people and his suggestion that the US should ban all Muslims for the time being both show he's dangerously willing to turn Americans against Americans in order to get elected. I'm not exactly sure how you would ban Muslims in any case; it's not like people have their religion on their passport.
But it's clear from the support both men are getting that there is intense anger at the establishment this time around. It's possible it is even sufficient to get through the barriers the parties have created to prevent non-status quo politicians from getting a chance to run in the general election. This election isn't right versus left; it's a debate about whether the country is a democracy or an oligarchy, even if Trump might have to be the unlikely face of the trampled masses.
Although I don't like the xenophobic nature of Trump's right-wing nationalism or the scary parallels it has with the rise of European fascism, the alternative is a continuation of two-party establishment politics. This means the continuing degradation of the United States into a corporate-owned, third-world country where a few own everything and control the political system.
A failure to enact real economic change this time around, with actual decent-paying jobs, would make people even more susceptible to right-wing populist demagoguery next time. Crazy as he sounds in this campaign season as he veers politically right in order to win the Republican nomination, look at his older quotes and you'll see Trump is traditionally a pretty liberal and moderate guy. If things keep getting worse, the guy taking advantage of all this public resentment next time might not just be silly ol' Trump.
Instead, it might be someone who wants to 'Make America Great' by creating a purity-based empire that will last for 1000 years...