Empirically, I see that it is impossible to get more than around 270 points in a day (the system stops giving credit after a while). And yet, when you look at the list of top weekly rep gatherers, it looks like number 1 has gotten around 500 points a day. How is this possible?
You can get at most 200 points in a day from upvotes. But bounties and +15 bonus for accepted answers are exempt from the cap. Hence, the total number of points one can get in a day is not limited.
For details, see How does "Reputation" work?