How was Mahatma's surname spelt?

There are a few references on the internet to Mahatma Ghandi, yet most references today spell his surname as Gandhi.

Is this the Mass Memory Discrepancy Effect in action or just a few instances of people being unsure hiw to spell it correctly so took their best guess?

The problem with the "simple misspelling" argument is that there really does appear to be many people who learned to spell it one way then suddenly, all within a short time span, all became aware they were "wrong" all along. If each individually were just correcting a lifelong misspelling, it would not happen to those experiencing it all at the same time. 

Spiritual

He was responsible for some of the greatest quotes the world has known:

An eye for eye only ends up making the whole world blind.

-- Gandhi

Influenced Mandela

It's well-known Nelson Mandela was influenced by Gandhi, and he no doubt would be greatly amused to hear there was another kind of connection today. This extends to the people too. Harris Majeke, South Africa's ambassador to India, said "While Nelson Mandela is the father of South Africa, Mahatma Gandhi is our grandfather". Gandhi was imprisoned in the same jail Nelson Mandela was, in Johannesburg in 1908. Nelson Mandela wrote extensively of his prison experiences - and refers to Gandhi being sent to jail 4 times in total.

To Western ears, the words sounds the same no matter how it's spelt, so even when written down both ways it would largely be accepted as correct without a second thought. Unusually, even if seen correctly then, later, incorrectly, because of the unusual "h" placement, Western eyes would still not see it as obviously being spelt wrong even though it had been pointed out as such earlier. So called "flip-flops" would be especially problematic.