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Trump won't win, but yes, he matters

Donald Trump is not going to be the next president of the United States.

This reporter is already on record pledging to eat a bag of rusty nails if the real estate tycoon with the high hair manages to snag the GOP nomination, much less takes down likely Democratic nominee Hillary Clinton next fall.

But Trump matters, in a major way.

Republican presidential candidate Donald Trump speaks during a campaign event in Phoenix, Arizona July 11, 2015.
Nancy Wiechec | Reuters
Republican presidential candidate Donald Trump speaks during a campaign event in Phoenix, Arizona July 11, 2015.

The Donald's rise to the top of many recent GOP polls tells us a couple of things. First , Republicans are not thrilled with the current field. And second, GOP primary voters love a shoot-from-the-hip novelty act, in this case one who breathes fire on immigration policy, the hottest of hot buttons for Republicans activists.

Trump talking about building giant walls to keep out Mexican "rapists" and "murders" while charging Mexico for every immigrant that makes it to the U.S. is the kind of stuff that the hard-core Republican base wants to hear.

They are much less attracted to former Florida Gov. Jeb Bush's compassionate approach that seeks a path to legal status for 11 million undocumented immigrants in the U.S.. Florida Sen. Marco Rubio has similar immigration problems with the primary electorate.

Read MoreTed Cruz: I 'salute' Donald Trump for discussing immigration

Novelty candidates such as Trump—think Herman Cain in 2012—have flared up in GOP primaries before only to fade quickly. Trump is likely to do so as well once the debates start and his relatively thin base of knowledge of global affairs is put to the test against more seasoned debaters.

But Trump is likely to play a much more important role than Cain or any of the other front-runner-for-a-day candidates in 2012. If the real estate billionaire uses the debate to savage Bush over his immigration and education policies, he could do a huge favor to the rest of the field, particularly Rubio and Wisconsin Gov. Scott Walker, who are the most likely GOP nominees after Bush.

Bush wants to spend his time on the debate stage proving that he is a mature, seasoned leader with a realistic plan to boost American wages and get growth revved up to 4 percent per year. That will be hard to do if Trump is constantly in his face.

And if Bush gets knocked down a few pegs, when the Trump boomlet inevitably fades, other members of the GOP field could be poised to snag the front-runner slot.

Read MoreWall Street doesn't fear Hillary...yet

Bush's secret weapon, of course, will be the over $100 million raised by his California-based Right to Rise Super PAC.

Once that PAC starts blanketing early state airwaves with television ads, Bush will be able to effectively respond to any debate attacks from Trump and keep his support from eroding too precipitously.

For those who think Trump has a real shot at winning the nomination, a little history lesson is in order. Republican primary voters often flirt with charismatic, fringe candidates but in the end almost always come home to the next-in-line, establishment figure. Think George W. Bush, John McCain and Mitt Romney.

Of course this could be the time that it's different—and widespread Republican anger at the Obama administration and a strong desire for someone to rip the president on a daily basis—could upend the usual dynamic.

But Republicans also desperately want to win the White House and they are not going to do it by nominating Donald Trump. It's more likely that Trump's numbers will dwindle following the debates and what are almost certain to be more incendiary comments. But before he fades, Trump may take a serious bite out of Bush and give a solid leg up to the rest of the field.

—Ben White is Politico's chief economic correspondent and a CNBC contributor. He also authors the daily tip sheet Politico Morning Money [politico.com/morningmoney]. Follow him on Twitter @morningmoneyben.