It depends. If NK attacked first, they would support him. If he reveals that there was credible info of NK planning an attack that would happen (really credible, like backed up by everyone in govt), they support him. If he does it for no apparent reason, they hate him.
I think that if he launches a preemptive strike over that sort of intelligence, people will support him in the short-term, but the general public will become divided quickly enough if it turns into a longer drawn-out war just as how Bush's bases solidly supported him until the 2004 elections and liberals were solidly against it.
