Why the media play along with Trump's presidential campaign

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

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

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

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

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

Trump launched his new book Crippled Americaon Tuesday and CNN covered itas 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 onlyTrump truly fascinates America.

For great swaths of the voting public, the flamboyant celebrity billionaire whonever lets a politically incorrect thought go unspoken is simply irresistible.

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

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

He easily outlasted the summer speculation that his popularity would fall with theautumn 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 centreof 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 weeksago it was still arguably Jeb Bush.

Neither of them polls like a front-runner in any early primary; neither has evenbeen 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 theargument. But the exotic candidates always crash and burn.Inevitably the partyestablishment ends up behind someone reasonable. Remember Mitt Romney in2012.

There is truth to that.

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

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

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

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

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

Shouldn't that be taken seriously?

Donald Trumpmay indeed crash and burn like other outside candidates beforehim. But he has already had an irreversible impact on the race.

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

Trump reset the race for them.

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

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

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

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

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

Consider how the early contests look: Iowa, New Hampshire and South Carolinacome 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 willbegin to consolidate behind him. Good for him, but that's still not the same aswinning.

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

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

There is something called the Party Decidestheory of presidential primariesthat holds that candidates must have the backing of the party establishment towin 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 getbehind a candidate.

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

Trump fits that description.

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

The Party Decidestheory only guarantees that the establishment wins in theend. It doesn't prevent disaster along the way.