With the Republican presidential nomination effectively sewn up, the main event is certainly soon to begin. Americans can expect the Super PACs representing both ends of the political spectrum to begin what promises to be a long and wearying war of words and images. While a nearly seven-month-long campaign seems inevitable, there is still hope that it will be at least somewhat civil, especially if the candidates weigh in favor of decency.

Because they can claim to operate independently of the candidates they support, PACs are free to engage in the most egregious of attack campaigns. And they typically do. With more than six months to build up steam, there’s a strong likelihood that political ugliness is going to reach a level never before seen — unless, of course, someone does something to stop it. The “someone” who has the power is each party’s candidate. While they can legitimately claim that PACs operate without their approval, the reality is that no PAC is going to deliver attack messages if its own candidate is out front about asking that they stop. After all, a candidate who could not manage to control his own supporters certainly could not be trusted to lead the country.

Now, before both camps get really wound up, is the time for Democrat and Republican candidates alike to stand up and announce that they won’t tolerate negative campaigning. If we must be subjected to more than half a year of presidential politics, keeping it civil is the least each side can do.