It was July 2016, and Labour MPs were running about like mice trying to put a bell on a cat. Jeremy Corbyn is the cat in this analogy. Sure, it makes sense now, with his grassroots popularity so assured that he has his own Christmas annual; his power within the party seems unassailable. Back then, these power dynamics were a bit less clear, as the party went from its uneasy internal truce of the referendum campaign to the recriminatory chaos that followed. Sorry, I’m getting ahead of myself: the self-justification should come after the mea culpa.

Owen Smith was emerging as the main challenger to Corbyn’s leadership. I wrote a column about him, headlined: “Decent bloke, good politics. But is that enough?” And I concluded: “Even if we think no leader could heal this party, Labour still needs a leader. It’s an effort to support someone on those terms … but [there was a familiar adage here that I’m a bit sheepish about] vote like you’ve never been catastrophically disappointed.” So that’s the first thing that was wrong with it: to explicitly say Smith didn’t have enough to recommend him then recommend him anyway, in some mad leap of faith, was lame.

But before that it was, plainly, a disloyal act for an MP to stand against Corbyn. I believed at the time that it was Corbyn’s weakness that had lost the remain cause: his failure to make a full-blooded case, his apparent diffidence and lack of industry. Looking back, it was more complicated than that. I still think that, had he been a passionate EU supporter, voiced that passion with the same certainty that characterised his opposition to student fees, to the same audiences, he could have won the vote to remain in the EU.

He could have spoken to the disaffection that drove the leave vote and offered better answers, more creative solutions than nationalism, less destructive paths than isolation. Yet I see now that he could only have done all that had he believed in it; that conviction and truthfulness are fundamental to his appeal, and if he’d squandered those by teaming up with John Major and Tony Blair for a pro-Europe variety performance, he might have won the battle and lost the war. Either way, that’s not the bit I’m apologising for: I’m still on Owen Smith.

I amassed a few quotes and anecdotes about Smith, all from allies of his. There was some murmuring, even from these supporters, about whether or not it had been his ambition to be leader all along, whether someone with his corporate background (he used to work for Pfizer) could take the post-2015 party with him, exactly how calculating he was, and I included all that. But I didn’t take on the fundamental question: that if he was of the left, what was he doing challenging Corbyn, rather than working with him?

Instead, I presented him as a new kind of Labour, distinct from the Kendall/Umunna scene yet with the same photogenic, affable sheen, sympathetic to the Corbyn worldview yet capable of coating it in such a way that normal people could swallow it. The only way all that could make sense was the idea that Corbyn was a busted flush, had proved himself to be incapable, and the best thing people of his persuasion could do for the party was to find someone a little bit like him to take over.

That, I could defend as a legitimate thing to think in the moment – especially given how close it was to the referendum. In retrospect, I felt a keen sense of failure. I was on the steering committee for Good Europe, I won’t trouble you with a description of it, suffice it to say that I didn’t think enough or do enough on its behalf. And it is reasonable, indeed, inevitable, that in the first stinging weeks of having politically disappointed yourself, you blame Corbyn. But what wasn’t reasonable was to join a consensus about the party leader’s incompetence tacitly, and not explicitly. It wasn’t a neutral character study of Smith; it was an attempt to accelerate the demise of Corbyn. I should have said that.

There were other errors, more of dog-sense than of morals; I praised Smith for the fact that he was untainted by the Blair years, and wondered aloud why he had such a low profile, quoting the MP John Mann: “The only problem is, who the hell’s Owen Smith?” Obviously, those were two sides of the same coin: he had an unblemished record because he’d only been in parliament six years; he had no base and little standing for the same reason.

That same inexperience led him to make idiotic remarks – he knew how to win battles because he’d fought off hordes to win his wife – and to think that being a nice bloke who didn’t significantly disagree with his leader was enough to make him a successful usurper and a realistic successor. Politics is easy to do but hard to do well; just because qualifications are unnecessary doesn’t mean experience won’t count; if you throw your lot in with the newbie, the PR hinterland fresh-face, you may as well choose David Cameron.

Wait, I don’t want to be writing another column this time next year, apologising for being unnecessarily harsh to Smith. He stood in good faith, under pressure from other MPs, and in defence of his own party, I believe, rather than out of personal ambition. The fault of discussing that challenge in a dishonest way was mine, not his.

Looking on the bright side, at least I didn’t plant my flag in the ground for Angela Eagle.

• Zoe Williams is a Guardian columnist