They often show support for a manned mission to Mars such as in a recent CBS news poll, yet a similar Rasmussen poll taken almost at the same time showed less than a third supported it. I believe the support for the general idea is there, but a lot of the support is soft and subject to question manipulation by doing things like implying a Mars mission will cost trillions rather than billions. You can also manipulate the numbers by forcing poll takers to choose one option or another rather than allowing them to pick all the options they support. Space advocacy groups tend to pump up the numbers by hand feeding info the general public seems to be unaware of. In short I have yet to see a poll I trusted either from the general news media or space advocates.

A rigorous poll should ask simply:

Do you support sending humans to Mars?

Do you support setting Mars as clear goal of the human space program?

Do you support modest increases to NASA's budget if that will get us to Mars? An alternate question form would allow choosing various levels of funding to get around the issue of erroneus perceptions of NASA's budget with the current level clearly identified.

Do you believe the XXXX (inflation adjusted) dollars NASA has spent on human space flight since Apollo was well spent?

Do you believe the YYY (inflation adjusted) dollars spent to land humans on the Moon was well spent?

How much of NASA's zzzz billion dollar annual budget for human spaceflight would you support spending annually to send humans to Mars?

How much of NASA's zzzz billion dollar annual budget for human spaceflight would you support spending annually to return humans to the Moon?

There are all sorts of additional questions I'd ask after those to determine how well the general public understands the issues around human spaceflight, but they should be asked only after the public is allowed to make gut level responses to general questions.

Regards,
Mark