It's easy to understand why Donald Trump wants to moderate a Republican presidential debate. He's happiest when he's the center of attention, and with his TV show on hiatus, hosting a televised debate will do just fine.

It's also easy to understand why Ron Paul and Jon Huntsman didn't hesitate to say "no thanks" to invitations to appear on Trump's debate show, which Paul's campaign described as "beneath the office of the presidency."

Both men continue to score high marks on the integrity meter. Unfortunately for them, that has not yet translated to similar rankings in popularity polls.

Rick Santorum jumped at the chance to participate in the debate, but given his poor showing in most polls and dwindling campaign funds, how could he not agree to more free time on TV?

Newt Gingrich also agreed immediately to appear in a Trump-moderated debate, once again showing his proclivity to swoon in the presence of big money and the things it can buy. Gingrich told NBC News that getting the Trump invitation was "like if Bill Gates called and said, 'Hi, I'd like to host a debate.' The correct answer would be, 'Yes.' You wouldn't say, 'Hi, I've got to check my calendar.' "

Maybe checking his calendar is why it took Mitt Romney so long to respond to the Trump invitation. Romney waited until late Tuesday to finally tell Trump no. His delay gave ammunition to those who believe his front-runner status has made him too cautious in declaring his positions.

Romney would have done himself more good by saying as early as Huntsman and Paul that Trump's sideshow isn't what their party needs.

No one has made that case as succinctly as did Republican strategist Karl Rove. "What the heck are the Republican candidates doing showing up at a debate with a guy who says 'I may run for president next year as an independent'?" asked Rove.

That's right. Even though Trump plans to declare a winner of his debate, he hasn't ruled out his own candidacy. The ringmaster likes to give his audience multiple acts to watch at once.

That Trump has grabbed some of the spotlight is meaningful. He obviously believes the GOP nomination contest has become boring. And the outcome of a boring process that produces a boring candidate to face one of the most exciting personalities in American politics today is predictable.

But is The Donald needed to shake things up? Not really. Herman Cain, who couldn't escape infidelity accusations, will soon be joined on the sidelines by others who find it increasingly difficult to raise money. The winnowing that comes with next month's caucuses and primaries will make the campaign livelier.

Trump's show, scheduled for Dec. 27, will serve only to show voters which candidates don't mind appearing in a circus act.