As this article by Rand Simberg lays it out, we now know enough about the space-related thinking of the three remaining major U.S. Presidential candidates to project their impact upon NASA, and especially on NASA's human spaceflight program.
The signs are troubling.
Senator Barack Obama is sounding like a supporter, but in vague terms that don't reassure anyone given his stated plan to delay the Constellation/VSE programs by five years and divert the money to education. His more recent statements indicate he's realized that would result in a "brain drain" and make it much more difficult to ever execute the VSE, but he has yet to address his contradictory plans and spell out specifics.
Senator Hilary Clinton has endorsed a continued robust human spaceflight program and left open at least the possibility of a meaningful budget increase for NASA. She has, however, not mentioned the Moon and Mars as destinations. Her advisor Lori Garver's speech to the AAS last November (which I blogged - see the archives) came closer to endorsing a continuation of the Bush VSE, but the candidate appears to have backed away from that. Pessimists fear we may see a repeat of Clinton 1 - a plus-up for Earth observation work, but a crippling of efforts to extend a human presence beyond LEO.
Senator John McCain has been explicit in endorsing the continuing drive for a human presence on the Moon and eventually Mars. The question in his case is funding. He's not committed to an increase for NASA, and his his plans for a budget freeze for all except military and veterans' programs might mean NASA must hobble along much as it does now, doing its best with assigned missions that are beyond its assigned funding.