Only trading volume on the final US 2028 presidential election results will count (e.g. Trump v Harris, ie no primary races).
Any real-money prediction market or betting platform globally counts.
I will exclude obvious wash trading insofar as I'm able to spot it (not an important factor in the 2024 election, but it might be in the future if these platforms continue to operate without fees).
I may add more answers to this market if new serious competitors emerge.
1,000I will exclude obvious wash trading insofar as I'm able to spot it (not an important factor in the 2024 election, but it might be in the future if these platforms continue to operate without fees).
I haven't looked into this much myself to verify, but my understanding is that the volume Polymarket reported for the '24 election was quite a bit inflated by wash trading: https://www.coindesk.com/business/2024/10/30/fortune-claims-polymarket-is-rife-with-wash-trading
(anecdotally, while the total amount wagered was very large (don't remember the # off the top of my head, but low 9 figures I think?), it was nowhere near large enough for the 3.6B in volume to seem plausible)