You may have to clarify the relationship between your skepticism about this process and your final sentence, I'm not sure I understand your point. While the budget is loosely a zero-sum game, individuals making the tradeoffs are motivated by political incentives, and among these incentives is popular support. Nor are we in any obvious 'stable attractor' in budget-space; new programs with new funding are included, and existing programs often have their share of funding increased, with each new budget. As I mentioned to ChristianKI, there is already precedent for NASA receiving a larger share of the federal budget than it does today (that is, the years 1962-2012). There doesn't seem to be any obvious disconnect between a demonstration of popular support and an increase in funding.
Further, this is not like voting; political support for NASA is on a continuum, rather than being a binary proposition. If only a small number of people show support (or a large number of people do), then an additional email still has value.
I'm not sure I understand your point.
I should have been more clear: do you believe that ceteris paribus a candidate who supports (more) space programs has an electoral advantage over one who does not?
The zero-sum game remark hints at the fact that "We should give a foozillion dollars to NASA" can be (and routinely is) countered by "No, we can use that foozillion dollars better by giving it to {somebody else}".
"The White House Office of Science and Technology Policy is planning ahead — way ahead. The agency wants you to email ideas for how "the Administration, the private sector, philanthropists, the research community and storytellers" can develop "massless" space exploration and a robust civilization beyond Earth."
This is beautiful.
"We are running out of adventures [...] the mountains have all been climbed, the continents explored, and the romance of sailing away on a tall ship to undiscovered islands is no more. What will fire the imaginations of the next generation?"
http://io9.com/white-house-seeks-advice-on-bootstrapping-a-solar-syst-1647619795