The problem was they could never quite forgive themselves for doing so and promptly began to destroy themselves over the issue of Europe, which served as a proxy for guilt over the regicide that they had committed. The fallout was a wonder to behold and I think if people are comparing the present situation to that, their memory serves them ill.
In the last gasps of the Major regime, cabinet collective responsibility had more or less completely broken down. Michael Portillo was amongst those who dishonoured themselves by publicly breaking with government policy yet clinging on to their cabinet posts, much in the way that Clare Short did over Iraq. Constituency MPs were also in open revolt, publishing their own anti-European manifestos whilst the stated policy of the government was to 'take Britain into the heart of Europe'.
The Tories, then as now, confused popularity with their own activists with that of the electorate. Thankfully they were and are wrong about that. Labour has since I can remember also been prone to this mistake. How else can you explain Michael Foot as a leader? Or Neil Kinnock for that matter? But they broke the opposition habit with Blair and this is the crucial difference: much of the Labour Party has never liked Blair because he is so obviously not one of them but they are mesmerised because he has given them what they were so desperate for - electability. In the elastic British constitution, it should never be underestimated how much authority a Prime Minister accrues if they win elections. Here Blair is more like Thatcher: it is forgotten how after 1979 the struggles she had in cabinet with the grandees and how the Falklands and the subsequent '83 election cemented her grip on power. And how, after a prime minister has been in power for two terms they simply make too many enemies to survive.
Blair is surely more like Thatcher in this respect? Any comparison with Major understates the sheer electoral achievements under the Blair leadership. Major won the '92 election for the Conservatives but they never gave him credit for it and in their disloyalty became turkeys voting for Christmas. Blair's achievements at the ballot box not only bear comparison to Thatcher's but far outstrip them.
This is the danger for the Labour party. Are they aware of how much the public disapproves of disloyalty? Do they not know that the public don't like Gordon Brown as nearly as much as they do? Here the comparison with Major is more appropriate: the Powellite-monetarist-Thatcherites backed Major because they thought he was one of them and turned on him viciously when they found that he wasn't. The same could be true of a Brown succession, which like Major's could take place without the electorate ever casting a vote. And when they get him, how long will it take them to realise that Brown is Blairism without the smiles, that he is at least as pro-market and pro-American as his predecessor? When they get it, they won't like it; they'll make a fuss and the electorate won't like that. Then who knows what could happen?