How would your perfect President and your perfect candidate differ?

[Donald Ian Rankin]

The perfect President would be the one who, having been elected, would run the country in the way you most approved of. For the sake of the argument, assume that s/he'd have sufficient personal popularity to get any laws or ammendments s/he desired passed, and wouldn't have to worry about reelection

The perfect Presidential candidate would be the person who you would most like to see win the Democratic presidential nomination. S/he would have to worry not just about whether a policy was good, but whether it would be popular; s/he'd have to compromise to the minimum necessary extent to win.

Some examples:

My perfect president would repeal the second ammendment and introduce roughly UK-level federal gun control laws; my perfect candidate would be cautiously in favour of gun control but believe in leaving it up to the states.

My perfect president would introduce a national health service, with health care free at point of use and paid for from general taxation; my perfect candidate would want to spend more money on medicare and medicade.

My perfect president would introduce a constitutional ammendment legalising gay marriage (see above claim about being able to pass any ammendments); my perfect candidate currently wouldn't, because it would fail, but would be in favour of state-wide measures to do so and would work towards making it federally viable as soon as possible.

My perfect president would be fairly single-minded; my perfect candidate would be a moderate who believed in compromise where possible.

What positions or personaly characteristics are there that you think a president should have but a candidate shouldn't, or vice versa?