You can find the contract source code and additional information here:
That seems like the sort of eventuality one should think through in advance.
It is possible to donate more than someone and still not be patron, e.g:
1. I donate 1000 eth, become patron #1.
2. Someone donates 1003 eth, he becomes patron #1, while patron #1 (me) is just forgotten (does not become patron #2).
3. Let's say places #2 and #3 already occupied too with donations of 999 and 888 eth.
4. I donate another 500 eth, so my total contribution now is 1500 eth, but I still do not make it into patrons list, despite I have donated more than anyone else.
5. Sad. Cevfefe.
I think our president at least supplied a bullet pointed one-sheet with his tax plan.