Republican presidential candidate Donald Trump talks with journalists during a rally against the Iran nuclear deal on the West Lawn of the U.S. Capitol on Wednesday. (Chip Somodevilla/Getty Images)

Imagine you are playing basketball and abiding by the generally accepted rules of the game: traveling, out of bounds, fouls, etc. Now imagine that the team you are playing against doesn't follow any of those rules. Also, there are no referees.

Or think of it like "Calvinball" — the "game" from the "Calvin and Hobbes" comic strip.

That should give you some sense of what it's like for the 16 Republican presidential candidates not named Donald Trump to run against the reality star/real-estate mogul. You can't win a fight with someone who isn't playing by the rules or doesn't, really, think there any rules — except the ones he makes up as he goes.

Look at the long succession of candidates who have tried to attack Trump and seen those hits rebound against them; Rick Perry and Rand Paul immediately jump to mind.

And, yet, three new attackers have stepped up to take a swing at Trump in recent days: Jeb Bush, Ben Carson and Bobby Jindal.

Bush's hits have been the most prolonged, attacking Trump as a chameleon who will say anything and do anything to get people to vote for him. In the wake of Trump's comments about fellow candidate Carly Fiorina's looks, Bush tweeted:

Fair enough. But, if you are scoring at home (and I am), it's hard not to see Trump's responses — that Bush is "low-energy" — doing more damage to the former Florida governor than vice versa. This Instagram video from Trump was particularly cutting:

Wake up Jeb supporters!

A post shared by President Donald J. Trump (@realdonaldtrump) on

Carson is relatively new to the attacking-Trump game. When asked Wednesday in California what differentiated him from Trump, Carson said: "Probably the biggest thing is I realized where my success has come from. And I don't in any way deny my faith in God. And I think that probably is a big difference here."

Then along came Trump. "You know, in all fairness, I don't know so much about his faith," Trump said of Carson on Thursday. "All of a sudden he became a man of great faith. I didn't notice this four or five years ago." Trump added that Carson, a world-renowned pediatric surgeon, was an "okay doctor." Very Trump.

Jindal, barely registering in the polls, seems to have decided that he might as well have a go at Trump, too — describing him on Thursday as an "unstable narcissist." (This is the definition of an attempt to "punch up;" even if Trump destroys Jindal in his inevitable retort, Jindal will get some attention, which he badly needs.)

While it's possible that one of this trio might get to Trump somehow and do him real political damage, I think that's very, very unlikely at this point. Why? Because no matter what they say, Trump will, well, trump them. Bush is boring. Carson isn't really religious or all that smart. Who knows what Trump will come up with about Jindal! (My prediction: "Jindal attacked me. He's an asterisk in the polls. Maybe he should worry less about Trump!" And, that's only 91 characters long!)

Point is, it's impossible for a traditional politician to one-up Trump unless they want to go into territory, rhetorically speaking, that only Trump can occupy. Sure, Bush can call Trump's comments about Fiorina "small" and "inappropriate." But Trump can call Bush a wimpy, charisma-challenged loser. Carson can wonder about Trump's faith. But Trump can say that Carson "makes Jeb Bush look like the Energizer bunny." Which one works better as a piece of negative rhetoric?

These other candidates can't use this kind of rhetoric because it doesn't really comport with their personalities.

(Also worth noting: Trump has a bullhorn waiting at his disposal whenever he wants it, thanks to cable TV. Because Trump = ratings, anytime he wants to call in or appear on a show, he will be welcome. Can you imagine Carson being allowed to call in to "The View?")

Engaging Trump in any way, shape or form is perilous. Yet, the other 16 candidates are now forced to do just that because of his pole position in both early state and national polling. But how do you beat someone who is constantly changing the rules of the game?

You don't.