From the comments...

It may be a half remembered anecdote - and thus embellished beyond recognition - but i seem to remember reading that the Glasgow ILPers who were part of the 1922 Parliamentary intake - Maxton, Wheatley, Kirkwood, Stephen etc - did more than chide themselves because they were convinced in later years that it was their votes that swung the leadership contest MacDonald's way against Clynes in '22.

If what they felt was true, then they contributed far more to Labour in Government then MacDonald ever thought imaginable.

Quoth the Ingrate in t'comments.

Yes, interestingly, reading about MacDonald for a talk I gave somewhere (Ramsay MacDonald: Bastard - was the title, for obvious reasons) I discovered that he came to power as the left-wing candidate. In 1914 he resigned the Labour leadership in order to oppose World War I. He was villified throughout, to the extent that John Bull magazine publicly revealled his bastardy.

In 1917, at a meeting in Leeds, MacDonald moved a resolution calling for the establishment of Workers' & Soldiers councils in the UK - MacDonald was calling for Soviets! Indeed, in his biography, Lloyd George called MacDonald "the British Kerensky."* Without a doubt, had Red Clydeside and the revolts of 1919 gone anywhere, MacDonald, would have come to head up a revolutionary government as a part of the left.

So, that's a moustacheod Scottish MP, who opposed a war coming to the forefront of the British left, only to cause mayhem by his tendency to renegadism. Where have I heard that one before?

Update Tsk! I forgot my own footnote.

*Intriguingly Alexander Kerensky, according to Wikipedia, is himself buried in Putney Vale cemetary, apparently, no Russian orthodox cemetaries in the US (where he died) would have him, blaming him for the Russian revolution.