All you need is to whip up a little sense of emergency granting you the power to act unilaterally and bob’s your uncle, you’re in business. There’s lots off bogeymen to choose from when you need to stampede the herd into cheering for you unilateral exercises of authoritarianism: global warming, Iranians, prolifers, tyrannical Catholic neanderthals bent on subjugating woman, homophobes, terrorists. Any of these (and various others) can be invoked as the Enemy Tunnelling Under Our Houses and you can usually get enough panic ginned up to get everybody cheering for you as you steal a few more lines from the Constitution.
After all, when you are anointed, you have lots of court prophets to run interference for you.