Just when you thought Donald Trump could not slither any lower after attacking immigrants he sneaks into a different swamp.

This time he attacked Senator John McCain, apparently for getting captured in Vietnam. Trump proclaimed McCain was not a hero after surviving five and a half years of torture.

“He’s not a war hero,” Trump said. “He was a war hero because he was captured. I like people who weren’t captured.”

Huh?

And where was Trump during the Vietnam War? We certainly know he wasn’t captured.

He was busy getting an exemption for his clubbed foot or a bone spur on his ankle, or maybe he cut his finger knitting or some such evasion.

In other words a draft dodger.

I know John McCain from interviewing him and dealing with him directly on the immigration issue. He is a bona fide hero and a proud Scots Irishman who loves his roots. He was the first Republican to show an interest at presidential campaign level appearing at an Irish presidential forum in 2008, in Scranton.

Then there is the war hero – the wounds that he suffered being captured and then tortured in the notorious Hanoi Hilton were beyond savagery and cruelty – it was downright sadistic. He refuses to discuss it.

He came through it like a hero and has been one ever since.

Last week he was one of the very few to take issue with Trump on immigrants from Mexico and whether they are all rapists and criminals.

He feels the immigrant dilemma deeply having seen the dead bodies in the Arizona desert of women and children desperately seeking a new life as he told us when we met him.

The Irish Lobby for Immigration Reform, which I co-founded in 2005, linked up with McCain on the immigration issue after 2005.

We hosted him several times and he spoke at immigration rallies in The Bronx for us and in Washington DC.

He was a hero then and now. I have watched backstage as an aide had to comb his hair and button his jacket. He cannot do those things for himself due to having his shoulders broken during torture.

Yet he never complained, was always courteous to a fault, privately very witty and not at all ego driven – and a hero.

Tinpan Trump is none of those things. He took $20 million his father gave him and turned it into a fortune. Easy to make a big fortune when you start with a small fortune.

Now he is playing at being president, this preposterous show-boater with the id of an oversize gnat and the ego of a monster.

Attacking John McCain is similar to the outrageous attacks John Kerry, another Vietnam hero, endured when he ran for president.

Are there no depths to which Trump won't sink?

I don't care to predict where he will go next. After immigrants come minorities.

Yes, those black mothers on welfare and the need to put limitations on how many meager dollars they get. The billionaire will take on food stamps I bet.

John McCain reflects everything great about America after giving it a lifetime of service.

Trump reflects himself in a trick carnival house mirror – big, bloated and out of control.

But can anyone in the GOP stop him?