I've come across a number of turning points in history which hinged on a single vote going one way or another. In some cases, that single vote might have dramatically altered the fate of nations - Trotsky's waffling and Brest-Litovsk, for example (although that's a matter for another forum).
I thought it would be interesting to see what others are out there. I propose any interested parties use this thread to:
[1] List cases where major policies were decided by, say, 1-3 votes that could plausibly have been reversed, invalidated, or otherwise eliminated.
[2] Explore the possible consequences of such Points of Divergence.
[3] Discuss the extent each scenario was nonsense and wouldn't actually have mattered.

[4] Reference existing timelines or threads that have explored this kind of POD.
I have three in mind of my own that I'll share, to begin with - all American:
The free west.
The treaty of New Echota (Cherokee removal).
Annexation of Santo Domingo.
I'll elaborate on those shortly.