That's one of the potential weaknesses in the idea. Ten trillion dollars might be too much to lose in a prediction market on how long it will take for Moscow to conquer Kiev, if it happens at all, conditional on Russia invading Ukraine; but is it too much to lose in a prediction market that could swing the US election?

Observably, so far, political spammers do not obtain ten trillion dollars per US election to spend on influencing it. Arguably this is only because they haven't found an effective way to spend that much money, and we should be very concerned that a mere 50 million dollars seems to have been enough to influence the prediction market results quite seriously in this case.

But that's not necessarily inherent to markets, even prediction markets. Foreign exchange rates were a major issue in our last election, because our rate of inflation was top in the world last year, but it isn't plausible for political parties to bet enough in forex futures markets to influence their predictions of those exchange rates—because banks bet almost 8 trillion dollars per day in the forex markets, so to intentionally maintain an irrational prediction in the market over the several months of the campaign, you'd need to be rich enough to expend roughly the entire world yearly GDP, and willing to lose it.

If sending spam required posting a bond set by the receiver, to be paid to the receiver if they decided the email was unwanted, I think you'd find that even political spammers did start to care a great deal about the cost. Until they cared, I'd set up domains with billions of potential receivers, each setting a ten-dollar bond. After the political spammers transferred their first few billion dollars to me, they'd run out of money.