It is obviously false and easily disproved. He has been called out repeatedly. But for some reason, Donald Trump keeps persisting with this fib.

One of the weirder quirks of Donald Trump's personality is his habit of telling easily disprovable lies.

Most politicians twist the truth to some extent. Many of them tell outright lies. Usually, they only do so when they don't think they will get caught.

Trump is more brazen.

Speaking in Pennsylvania today, he repeated one of his favourite fibs — a seemingly innocuous boast about a policy designed to help America's veterans.

"I got it approved. Veterans Choice," the President said.

Veterans Choice is a healthcare program that allows American military veterans to see private sector doctors, outside the US Government's Veterans Affairs system, if they would otherwise have to wait too long for an appointment.

Trump has repeatedly taken credit for creating the program, often saying he accomplished something other politicians had been trying to do — without success — for decades.

For example, at a rally in May he said: "We passed VA Choice and VA Accountability to give our veterans the care that they deserve, and they have been trying to pass these things for 45 years."

CNN reporter Daniel Dale has been keeping a running tally for months and says Trump has now made the Veterans Choice boast more than 80 times.

Donald Trump speaking in Pennsylvania today. Photo / AP

Earlier this month, the President added more detail to his story, saying he came up with the idea for Veterans Choice during the 2016 election campaign.

"I said, you know, 'I have a great idea. I've been thinking about it a lot'. This was during the campaign," Trump said.

"And I came back to my people, I had experts, and I said, 'I have a great idea. These lines for the veterans are too long. It takes them three, four weeks sometimes to see a doctor. I have a great idea — let's let them go outside, go to a private doctor. We'll pay the bill, they'll be all fixed up all perfect, and they can do it immediately and we'll pay the bill'.

"And I thought, I said, 'Man am I smart. I am the smartest guy, to think of that'. So I went before this panel of experts that were with me working on things, and I said, 'How do you like that idea?' And they said, 'Sir, we've known about it for about 40 years, but we've never been able'.

"But here's the thing. We got it done. Nobody else could get it done. Nobody else."

Here's the actual thing. Donald Trump did not pass Veterans Choice.

The legislation was actually passed under his predecessor Barack Obama in 2014 before Trump was even running for president. He had absolutely nothing to do with it.

When Trump supposedly came up with the idea of letting veterans see private doctors outside the VA system, and a panel of experts supposedly praised him … the program already existed.

Veterans Choice was actually passed under Barack Obama. Photo / AP

Compounding the lie, Trump has used Veterans Choice to attack the late Republican senator John McCain, who died last year after battling a brain tumour.

"McCain didn't get the job done for our great vets and the VA, and they knew it. That's why when I had my dispute with him, I had such incredible support from the vets and from the military. The vets were on my side because I got the job done. I got Choice," the President said in March.

"Choice. For years and years, decades, they wanted to get Choice.

"For many decades, they couldn't get it done. It was never done. I got it, five months ago, I got it done. Choice."

In fact, McCain co-sponsored the bill that created Veterans Choice, along with independent Senator Bernie Sanders (who is now running for the Democrats' presidential nomination).

So, to summarise, Trump has claimed more than 80 times that he was the one who created Veterans Choice when it was actually signed into law years before he became president.

And he has attacked a dead senator, McCain, for failing to deliver the program when McCain was actually the one who got it passed.

I will offer one potential innocent explanation for what is, by all appearances, an extraordinary display of dishonesty.

It is possible Trump is just extremely confused about his own record.

He did sign a law making changes to the Veterans Choice program in June of last year.

Under the original legislation, veterans could see private sector doctors under two conditions: if the wait for an appointment in the Veterans Affairs system was going to be more than 30 days or if they were forced to drive more than 65km to a VA facility.

The requirements are now either a wait of 20 days or a drive time of 30 minutes.

It is conceivable that Trump mistakenly believes the law he signed created Veterans Choice when it really just tweaked the program and expanded access to it.

Of course, that explanation does not account for Trump's claim that experts told him, during the election campaign, they'd never been able to get the idea passed when it was already law at the time.

Nor does it explain why the President's staff have allowed him to repeat the incorrect assertion almost 100 times in public.

Ironically, the bill tweaking the program — the one Trump really did sign, and really could take some credit for — was named after McCain.

"I want to thank John McCain, whose idea this was originally," Republican Senator Johnny Isakson said after it passed.

Republican war veteran and former senator John McCain. He died last year. Photo / Getty Images

"John is the one who started the movement towards Choice, and he deserves the credit for it."

As far as Trump is concerned, the credit belongs to him.