One way such a politician could do good is by helping direct funds to MIRI.
How?
I wonder if a good way to do good as a politician would be to try to be effective and popular during your term, then work as a lobbyist afterwards and lobby for causes you support (like x-risk reduction, prediction market legalization, and whatnot).
How?
I suspect my model of the method used to allocate government funding may be oversimplified/incorrect altogether, but I am under the impression that those serving on the House Science Committee have a significant say in where funds are allocated for scientific research. Given that some members of this committee do not believe in evolution and do not believe in man-made climate change, it seems that the potential social good of becoming a successful politician could be very high.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.