I feel like I hear the Many Worlds interpretation of QM used to ground probability in indexical anticipation. For example, saying there's a 2/3 chance Obama wins the next election means that of some large number of future universes, Obama wins the next election in 2/3 of them, and you don't know which one to expect to be in, insofar as that question is even meaningful.
But universes branch out based on the behavior of individual particles, not interesting human-level events like elections. Let's say we copy the universe, run one copy until the election, and note Obama wins. Then we're going to run the other copy, which is still stuck in June.
For Obama to win the election, something interesting must be different. Let's take even a very small event that snowballs - maybe a piece of dust gets in the engine of Obama's car, the car breaks down, he's late to an important rally, and that puts him in such a bad mood that he makes a gaffe which costs him the election.
But for QM to move something as large as a piece of dust takes billions of particles simultaneously ending up in a wildly improbable position. If we don't routinely see dust specks jumping from place to place for quantum reasons in experiments, we shouldn't expect it to happen in Obama's car either.
So this suggests that there's not a 1/3 chance Obama will lose the election in the second copy of the universe, but more like a 1/3^^^3 chance he will - and anything that takes more than a dust speck of difference will be even more unlikely. If every possibility instantiates in a universe, there will still be a couple of universes where Obama loses, but over timescales like that of human history we will see an overwhelmingly large number of universes that are completely identical on the human level - ones where electrons ended up in slightly different positions but no harm done - and those that differ significantly in things like politicians will be such a tiny fraction we barely even have the numbers to express them.
Is my understanding here correct?
And when you answer this question, I've got several hundred more!