Across the world, campaigning is under way for those interested in standing for the American presidency.

The legacy on the domestic front is, no doubt, “Obamacare” — the attempt to expand medical insurance cover beyond those who can afford to pay for private cover.

The American medical insurance industry is fairly vicious. Many years ago, for example, following the entry into force of the Free Trade Agreement, its lobbyists had the audacity to challenge Canada’s universal health care coverage — managed at the provincial level, increasingly on a nominal payment basic — as a barrier to its ability to compete within Canada.

That US President Barack Obama got as far as he did on this in his first term is nothing short of miraculous — even though the rest of the world finds it bemusing that the US is pretty much the only overdeveloped state that doesn’t offer universal health care.

As his second and final term winds down, he seems to be seeking — with equal difficulty — to secure his legacy on the foreign policy front. The rapprochement with Cuba proceeds, to the fury of the Cuban exile community in the south. Losing the Democratic Party, no doubt, some of its Latino support base.

And now there is the deal with Iraq — teetering on the edge, with scepticism within his own party and yet more fury across the aisles. Couched in terms of what many see as an unforgivable shift away from unquestioning support of Israel’s position on the matter.

Oddly, none of these issues — contentious primarily within the United States but fairly common sense to everybody else — seem to be playing out much in the battle for the presidential candidacy.

No. The terms of that battle have been marked by the astonishing ascendancy of Donald Trump among the Republican Party’s support base. All polls put him way ahead over every other potential candidate. Outside of the United States, everybody is watching with fascinated horror.

He comes across as arrogant, crass and uneducated — his evident ability to make money aside. He says the most offensive things.

About immigrants — as though all Americans, with the exception of its indigenous peoples, are not themselves immigrants. About women. About China — which, holding most of America’s debt, behaved impeccably during the financial crisis when it could arguably have chosen to do otherwise if it weren’t a rational actor, able to see how its own future depended on everybody extricating themselves from that particular mess.

And his policy positions — if they can be called such, seeming more to pander to pure populist fears — are completely crazy. Look at his position that all seven million or so estimated illegal migrants be deported. How and to where remains unclear.

But this has brought him the public endorsement, finally, of America’s white supremacists. From the Klan to the broad spectrum of neo-Nazi organisations who are so worried about the fate of the white population.

Even the unbearable Fox network seems a bit shocked — when he and people like him are exactly what Fox has always promoted.

Fascinated horror. Who are these Americans who support him? Can it possibly be true that they are the “silent majority”?

How could America tolerate such a drastic shift — from a fairly thoughtful presidency to… that? It’s unbelievable really.

L. Muthoni Wanyeki is Amnesty International’s regional director for East Africa, the Horn and the Great Lakes.