For Gaius Julius Caesar, Republican precedent was never an obstacle to his personal ambition. In 59 BC, after a bitter political battle with Cato and his allies, and a bare-knuckles political brawl over a land bill, Caesar began an unprecedented five year term as governor of Spain. Later, his famous campaign in Gaul started with a blatantly illegal action, a conflict with a Gallic tribe not under Roman rule, which violated a law that Caesar himself had authored. His most famously unprecedented action came in 49 BC, when he crossed the Rubicon, violating Roman law, custom, tradition, and core political ethos by bringing soldiers into the province of Italy. Being elected dictator for life, of course, bent Roman traditions completely out of shape, until a cabal of outraged Republicans assassinated him on the steps of the Senate.
And that's not even an exhaustive list of all the times Caesar bent or broke Roman law and tradition. He was, though, hardly unique for his time. Roman leaders had cut themselves loose from the constraints of the Roman state, leading to the epic clashes among great men (Caesar, Pompey, Crassus, Clodius, Milo, Cato, Cicero, Catiline, etc. etc.) that finally trampled the Republic into the imperial dust.
There are other times when law and tradition grow too weak to constrain the ambitions of the notable and powerful. These are never good periods in which to live. For example, the justification for Henry IV's seizure of power from Richard II was pretty threadbare. The fact that Henry re-wrote the rules of dynastic succession to his liking led to a period of political instability that didn't end until the War of the Roses.
Of course, you might be looking for a more contemporary example. Look no further than the last several years of American history. Dick Cheney becomes the first co-president. George Bush's Justice Department pushes a ludicrous "unitary executive" argument for making the President unanswerable to the other parts of the federal government. And this week, John McCain spits in the face of decades of presidential political tradition, announcing that he won't debate his Democratic opponent, nor will his laughably underqualified running mate (another precedent-breaker) debate her counterpart. And he's "suspending" his campaign, something unheard of in American politics, especially since he continued campaigning.
No, I'm not saying we're living in the last days of the American republic. However, I am saying that we should be more than worried when leaders don't feel the weight and thickness of the constraints, both formal and informal, that should bind them.
We should, as citizens, stop pretending that we have no responsibility for what happens, or lie to ourselves that we live in times so extraordinary that the rules no longer apply. These rules--durable because they work--evolved over two centuries, including foreign invasion (the War of 1812), one of the bloodiest civil wars in any country's history, global wars, recessions, depressions, and a period when an impacably hostile foe was pointing thousands of nuclear weapons at us. Even the newer traditions, such as presidential debates, deserve to be treated as sacred rites of American democracy. The rules of American politics are not conveniences, and we should be very frightened of men and women who treat them as such.
But we should do more than recoil with fear or disgust. We must act, so we don't stumble further towards the precipice. (It may be far away, but it's still there.) You're citizens of a democracy--you can figure out what to do next.