Political outcomes, even ones that may seem inevitable or even historically preordained, are always less clear in advance than they are in retrospect. Coleridge compares the problem to sailing on the ocean at night. Others invoke the fog of politics, likening it to the fog of war. Not to understand that politicians fear the unknown is not to understand politics. It’s why MPs mostly hate general elections. It’s why would-be leaders often bottle a contest they should win. It’s why those who have power try so hard to hold on to it, and why resignations are almost always messy and acrimonious.

The mechanics and tactics of Zuma's attempt to negotiate a face- and cash-saving deal are electrifying

Enoch Powell’s fatalistic observation that all political careers end in failure is often quoted in this context. It will probably be invoked about the ANC, now that Jacob’s Zuma career has crashed and burned. It will doubtless make an appearance as part of Theresa May’s eventual epitaph. It waits, ready at hand, to be cited in any number of future political obituaries of the great and the not so great.

The trouble with Powell’s words, though, is that they explain everything in general and nothing in particular. To an essentially pessimistic Tory like Powell, folly and failure were wired into the political DNA. For such people, no great political or governmental project ever really works. Optimism about the human condition is an illusion. Man came from dust, and will return to dust. As Powell put it in the words that follow immediately after the famous ones about failure: “That is the nature of politics and of human affairs.”

Play Video 3:04 Jacob Zuma: South Africa’s scandal-struck president resigns – video

But failure – and day-to-day politics in general – is far more interesting than Powell’s pessimistic determinism allows. Political failure is always relative, not absolute. It is as many-sided and as nuanced as success. Failure can be dodged and deferred, as the careers of May and several of her ministers show. Failure can also be fought every inch of the way, as Zuma tried to do. One may or may not approve of either May or Zuma, but there is something humanly impressive and authentic about their attempts to postpone what, in the larger arc of history, is too often simplistically dismissed as an inevitable outcome.

The battle that has been going on in the ANC is hand-to-hand politics at its most compelling. Such moments deserve the detailed attention of minute-by-minute accounts, not banal generalisation. To treat the South African power struggle, as liberals may be tempted to do, as simply a battle of right against wrong – or, Powell-like, as an ultimately futile exercise conducted by mortal fools – is to belittle it.

The attempt to remove an elected leader is the most dangerous challenge that any democracy can ever face. These are rare moments, and they do not always go according to plan. A Zuma-style ousting doesn’t always happen when or how it should, or tidily. But if democratic politics matters at all, as most people living in democracies still think, then such moments matter more than most. We have a dog in this fight.

Facebook Twitter Pinterest The Irish Home Rule leader Charles Stewart Parnell is removed from the House of Commons. When cited in a divorce, he fought - ‘like Zuma is doing today’ – to stay on as leader. Photograph: Rischgitz/Getty Images

Though Zuma’s ultimate fate seemed a predictable one he fought deep into extra time. The mechanics and tactics of his attempt to stay on, and then to negotiate a face- and cash-saving deal, were electrifying. The implications at every turn are supercharged for both sides and for his country. Cyril Ramaphosa’s determination not to allow Zuma a compromise was heroic. That doesn’t mean Ramaphosa is in all things a hero. It just means that this is a moment with large national consequences.

Endgames always compel. Hitler’s rant against his underlings in the 2004 movie Downfall is probably more famous now in its multiple online parodies about football or new video games than as a depiction of the events in the Berlin bunker in April 1945. But the moment when anyone’s world and certainties implode is a universal fear. Very few politicians leave office at a time or in a manner of their own choosing. “He has gone out with all the bands playing,” his secretary wrote of Stanley Baldwin’s resignation as prime minister in 1937. “For many months he has been longing for this release.” It is hard to think of any successor of whom the same could be said.

At no time in this drama was it clear if the caucuses, negotiations and political moves in South Africa would succeed. Ramaphosa would not have launched his challenge if he lacked the numbers in the party and parliament. But the element of uncertainty at such moments should never be understated. Such events are contingent. Things can go wrong. The outcomes depend on multiple unpredictabilities, not just pure calculation by the ANC high command. The words used and the tone adopted by the protagonists will shape the outcome.

When the MPs of the Irish Home Rule party holed up in a Commons committee room for six days in December 1890 to decide if the hitherto indispensable Charles Stewart Parnell could remain as leader after being cited in a divorce, they did not know whether he would stay or go. Parnell fought every inch of the way, as Zuma did today, not least because he chaired the meetings – but also because much Irish opinion wanted him to hang on. In retrospect, it is obvious Parnell would lose. But not so obvious at the time.

Play Video 0:52 Jacob Zuma steps down after defying ANC orders to leave office – video

When Neville Chamberlain’s backbenchers revolted against him in May 1940, no one knew who would emerge from the crisis as prime minister in his place. Chamberlain – and, it seemed, the Labour party – preferred Lord Halifax, a proponent of a negotiated peace. Halifax came as close to the highest office as anyone has ever done in British history without actually getting it. In one of Winston Churchill’s accounts, it was only Churchill’s own prolonged silence in a meeting with Chamberlain that forced Halifax to speak first and decline the prime ministership, thus bringing Churchill to power.

Nothing is certain in politics, and that even includes political failure. As an old man in his 80s, Powell told an interviewer that his famous dictum about political failure did not, in fact, apply to his own career. True, Powell no longer had a parliamentary seat or ministerial office, but “I see myself being proved right”. He was referring to his opposition to immigration and the European Union. Who, looking at the politics of modern Britain a quarter of a century later, can deny that he had a point?

• Martin Kettle is a Guardian columnist