Without any context: said of a person of strong moral and intellectual strength.
Here is a bit of context. I am not powerlerner.
Saying that he knew the Illinois Democrat well from their time together on the campaign trail, Biden said ofObama, he "has the judgment, he has the intellect, which no one doubts, and I guarantee you he has the steel in his spine to lead this country of ours out of the deep hole we have dug ourselves into." [snip] Obama's spine of steel, McCain's mind of mush - City Hall - Election 2008