What awaits Trump: Closer scrutiny

Trump-mentum continued through the weekend with a pile of new polls showing the braggadocio billionaire leading in New Hampshire, close in Iowa and at the top nationwide.

But there are several reasons to be skeptical that Trump can keep it up into the fall, much less until actual voting begins next year. There are two main problems: An apparent lack of grassroots organization and a set of policy views that remain either unfocused or in direct contradiction to Republican orthodoxy.

First the good news for Trump. NBC/Marist polls over the weekend showed him in the lead in New Hampshire and a close second in Iowa, a state that usually demands fealty to traditional GOP views on abortion and other social issues where Trump is decidedly out of step. And a CNN/ORC poll release Sunday put Trump at 18 percent nationally, barely ahead of Jeb Bush at 15 percent for the top spot among Republicans.

Read MoreTrump plays: Election could boost these stocks

Republican presidential hopeful businessman Donald Trump speaks to the press following a rally on July 25, 2015 in Oskaloosa, Iowa.
Getty Images
Republican presidential hopeful businessman Donald Trump speaks to the press following a rally on July 25, 2015 in Oskaloosa, Iowa.

Trump's numbers went up, not down, following his harsh comments about Sen. John McCain. That shows just how generally angry GOP primary voters are and how little they care about what the establishment thinks.

More CNN/ORC numbers released Monday explain why Trump is doing so well, beyond his own charisma and media savvy. Only 30 percent of voters nationwide believe their views are being represented by government officials in Washington. Among Republicans, the number is just 16 percent.

That means the GOP is hungry for an outsider candidate unafraid to take shots at other more established candidates, especially those with heavy Washington experience. At this early stage it hardly matters what Trump actually believes on policy beyond his red-hot rhetoric on immigration, which is closely aligned with activist Republican primary voters.

Read MoreWill Hillary's econ speech bring together Democrats?

But it will matter at some point. And probably fairly soon when the debates begin in August. Because then candidates with more traditional GOP views on abortion, marriage and other issues will be able to draw sharp contrasts with Trump.

Nailing down exactly where the real estate magnate stands on a range of issues is quite difficult. His campaign website has no policy tab and the campaign apparently lacks a policy director. Such nuts and bolts stuff does not matter when a huge personality like Trump is riding a wave of public support. But it will matter when the debates come around and voters start to really weigh what candidates would do in office.

Trump has been a Democrat in the past. He has supported a huge surtax on the wealthy along with abortion rights. He's now a Republican and has shifted away from any tax increases. But his overall policy approach is remains a bit of a muddle.

Other GOP protest candidates like Herman Cain faded fast when their policy views and knowledge came under closer scrutiny. Trump has rhetorical and media skills well beyond other GOP flameouts in the past. And he is a very smart guy. But he will be heavily tested.

Another critical issue is his lack of traditional campaign infrastructure in early voting states, particularly Iowa. At the moment, Iowa Republicans are flocking to Trump's events and thrilling at his bold talk.

But getting those Republicans to actually show up and caucus for Trump six months from now will be a very different story. Typically, campaigns spend months building a network in Iowa to identify caucus goers, persuade them and get them to show up. It's not impossible that Trump's cult of personality could render the traditional approach obsolete. But it's not very likely.

Read MoreTrump won't win, but yes, he matters

And big waves like Trump is enjoying now rarely last long. And once they fade it takes money, organization and a relentlessly clear message to stay at or near the top and close the deal when the voting begins. It's still much more likely that Republicans eventually come home to Bush or Scott Walker or Marco Rubio than it is that they nominate Donald Trump.

But anything can happen in politics and a Trump vs. Hillary Clinton general election could actually happen. And wouldn't that be wild.

—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.