It's a truism in American politics that everyone believes the other side is completely nuts. Delusional. Certain about facts that just simply don't exist.

This is a simplification, sure, but it's also kind of a meta-statement about a different serious problem in American politics, which is the myth of "balance" and an insistence that "both sides do it."

But both sides don't do it. The fact is that only one political party right now seems to exist in a world of fantasy and delusion, not both.

This comes to mind at this moment, because I am considering the possibility that Donald Trump might actually make it to the end of the Republican primary season as the winner, the nominee of the Delusional Party. Or, just as bad, someone like Ben Carson or Carly Fiorina or Jeb Bush, all of whom have demonstrated their disconnection from reality in recent days.

Bush, for example, had perhaps the biggest laugh line of the campaign so far when he said of his brother George W. at the debate last week, "There's one thing I know for sure: He kept us safe." Um, what now? The president who presided over not just 9/11 but also the disaster that was Hurricane Katrina and the deaths of thousands of US servicemen in Iraq kept us safe?

As if to prove that he's more qualified than anyone to lead the Delusional Party, Jeb the next day tweeted out the famous picture of his brother literally standing on the rubble of the World Trade Center where almost 3,000 people died because George W. ignored warnings about al Qaida all the previous summer.

I mean, I know that Jeb, as an actual politician who has won elections and governed a state, is probably upset that relative novices like Trump and Carson are overshadowing him right now, but come on, that seems like a lot even for a member of the Delusional Party.

Fiorina, too, is a novice – though not for trying. She ran for senate a few years back and got blown out. But she is no less a member in good standing of the Delusional Party.

At the debate, she got a lot of screen time but spent much of it saying things that just aren't true. The one getting attention since then is that she claimed to have seen one of the ant-Planned Parenthood videos that showed a Planned Parenthood doctor saying of a squirming baby, "We have to keep it alive to harvest its brain."

This scene, of course, does not exist in the videos. Or in any other video the Fiorina campaign could produce. It didn't stop her from insisting it was true, though.

But it's not just abortion where Fiorina expresses her delusions. Her well-received (on the right) views on climate change, for example, are completely false. And her contention that her tenure running HP – a tenure that ended with her being forced out and with HP shareholders kind of screwed – makes her qualified to be president is obviously delusional.

Which brings us to Carson, currently number two in the Delusional Party's polls. Carson did us all a solid, and I mean that sincerely, when last week he beat down Trump's anti-vaccination point of view, correctly noting that there's no connection between vaccinating children and autism.

But Carson still has two feet firmly planted in the Delusional Party, with a history of false statements and appeals to the Republican faithful not grounded in reality. Often, he does this by saying things as an African American man that white candidates can't say for fear of being called not just wrong but also racist. Among these are Carson's occasional false claims that there are more black men in the criminal justice system than in higher education, for example.

He also repeats the myth that Margaret Sanger, a birth-control advocate and founder of Planned Parenthood, was a racist eugenicist who wanted to eliminate the black race. I am guessing that if that were true, it would surprise Sanger's friends and allies, like W.E.B. du Bois and Adam Clayton Powell.

But top of the list has to be what he said this past weekend about the idea if electing someone of the Islamic faith to be president. Claiming Islam is inconsistent with the US Constitution – and no, I don't know what that means, either – he insisted that no Muslim should ever be president. And maybe not in Congress, either. "It depends on who that Muslim is," he said, I guess meaning only the good ones.

That last bit was all, of course, in response to Donald Trump, one-time leading spokesperson for the "birther" movement that believes President Barack Obama was not born in this country and is probably also a "secret Muslim." Indeed, polls of Trump's supporters consistently show a huge chunk of his constituency believes these demonstrably false claims to be true.

Trump was asked last week about alleged Muslim training camps ("How do we get rid of them?") in the US by a man who claimed that Obama "is one" and "not even American." I'm willing to give Trump the benefit of the doubt that his "We're going to be looking at that" answer was about getting rid training camps, not about getting rid of Muslims in general. Although, of course, there are no Muslim terrorist "training camps" on US soil.

But Trump's failure to correct the man's statements about Obama drew attention. And, of course, it should have, since Trump has expressed exactly those kinds of beliefs before himself.

And this is really the thing that freaks me out here. Trump's support seems to be built almost entirely on fantasy. When his supporters are willing to believe that "a twice-divorced casino mogul," "an unrepentant serial adulterer" who can't name a bible verse, is the one to "change the White House back to Christianity," the delusion has reached critical mass.

And I could go on. People like Paul Krugman have made whole career out of pointing out that the modern Republican party believes untruths about economics and foreign policy that I just don't have space to get into here. And we just went through a whole summer of trying to deal with people who believe that the flag representing secessionist traitors is really a symbol of deep patriotism and fighting the belief that the US military was invading the "hostile" territory of Texas. If I had to write a column every time the Republicans showed their delusions, my fingertips would be worn down to bloody stumps.

And here's my actual biggest fear – not just that it will keep going like this, but that it will get worse, that we might actually end up with President Trump, king of the Delusional Party.