Why the media play along with Trump's presidential campaign

Presidential candidate Donald Trump will host NBC's Saturday Night Live this weekend and you can bet the audience will be "uuuuge!"

That will make both the candidate and the network happy, but who benefits more is impossible to say; the symbiosis between them is seamless. 

It confirms again that Trump's show-business talents are his most formidable political advantage.

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Until this week when he bought some radio ads, he'd spent not a single nickel on campaign advertising.

Why would he, when so much was available to him free? 

Trump launched his new book Crippled America on Tuesday and CNN covered it as though he`d just landed a spaceship on Mars.  

For 35 minutes he had free rein to trash his political rivals. Marco Rubio: "His credit cards are a disaster." Ben Carson: "Weak on immigration and he wants to get rid of Medicare." Jeb Bush: "No energy."

• Clips from outspoken Republican presidential hopeful's news conference promoting his new book

Any other politician would kill for that opportunity but Trump gets it because only Trump truly fascinates America.

For great swaths of the voting public, the flamboyant celebrity billionaire who never lets a politically incorrect thought go unspoken is simply irresistible.

Why, then, is the conventional wisdom still that he cannot win the Republican nomination for president?

Why casually dismiss such a uniquely gifted contender when he has consistently and vastly exceeded expectations?

He easily outlasted the summer speculation that his popularity would fall with the autumn leaves. He has been the most durable front-runner in the race for months.

As the conversation moves on to the early primaries he's right at the centre of it: Will Trump win Iowa? Will he win New Hampshire? What about South Carolina?

But "Will he win the nomination?" is not for serious discussion.

The favourite for the nomination is now, supposedly, Rubio. Two weeks ago it was still arguably Jeb Bush. 

Neither of them polls like a front-runner in any early primary; neither has even been within spitting distance of Trump or Ben Carson in a national poll. 

But, we're told, we've seen it all before.

Republicans always have an early flirtation with exotic candidates, goes the argument. But the exotic candidates always crash and burn. Inevitably the party establishment ends up behind someone reasonable. Remember Mitt Romney in 2012.

There is truth to that.

But it still feels as though the real story of this campaign is invisible inside the Washington beltway. 

What's shaping up is a truly titanic clash for Republicans. On one side are millions of insurgent, Tea Party infused, conservatives; on the other is the Republican Party establishment.

The insurgents are the Republicans who stood up and cheered last month when told that their party's most senior man in Washington, House Speaker John Boehner, had been kicked out of his job by conservatives in his caucus.  

They're the sort of Republicans who worked against the second most senior House member, Republican Majority Leader Eric Cantor, and defeated him in a primary election last year.

And now they want to take down whomever the party establishment thinks should be its presidential nominee. 

Shouldn't that be taken seriously?

Donald Trump may indeed crash and burn like other outside candidates before him. But he has already had an irreversible impact on the race.

With his deep pockets, mega celebrity and un-PC mouth, he was the early champion of those who care more about upsetting the Republican Party than putting a Republican in the White House.

Trump reset the race for them.

Rather than a string of insurgents taking turns at challenging the establishment's choice for nominee, as happened in 2012 with Romney, Trump defined the campaign as having two distinct lanes of candidates. Each lane aims to produce a contender.

In one lane are the insurgents: Trump, Carson and Ted Cruz. Together they are consistently supported by more than half of the Republicans polled.

In the other lane is the crowd that includes Rubio, Bush, John Kasich and others who are vying for the establishment endorsement.  

The strongest contender from each lane will be determined in the caucuses and primaries that begin in February.

A face-off between those two contenders is not inevitable, but it seems more likely every day and it could be messy.

Consider how the early contests look: Iowa, New Hampshire and South Carolina come up first. Trump and Carson top the polls in all of them.

If Rubio finishes third in all three, but first in his lane, the establishment vote will begin to consolidate behind him.  Good for him, but that's still not the same as winning.

If Trump or Carson or both continue to roll, Rubio could enter the Ides of March primary in Florida without a convincing win under his belt and still running behind Trump in his home state.  

What happens then is anybody's guess but whatever it is, it's unlikely to be smooth.  

There is something called the Party Decides theory of presidential primaries that holds that candidates must have the backing of the party establishment to win a presidential nomination.

That theory reminds us that the party has real power.

Party leaders are themselves a small percentage of voting delegates. They will get behind a candidate.

They also control how the rules of the nomination process are interpreted when there is a dispute. That's a power they could use against a candidate deemed unelectable and unfaithful to the party's agenda.

Trump fits that description.

But if these are the reasons for squashing the hopes of possibly millions of Republicans, then the Republican establishment may be courting a catastrophe the likes of which hasn't been seen since the Democrats went to Chicago in 1968. 

The Party Decides theory only guarantees that the establishment wins in the end.  It doesn't prevent disaster along the way.