“Brinkmanship” or “Brinksmanship”?

Interestingly, the latter Google search yields 4.4 million hits, while the former yields just 1.9 million hits, yet the Google search for the latter redirects to that for the former, unless you tell it not to. Apparently, either term is acceptable. I find “brinksmanship” more euphonious, perhaps due to the parallel with “marksmanship.”