The only way to keep it from swinging back is to move to a totalitarian state. Even then, most people will rebel against it. The reason is that the left is built on a disparate base. There are actually very few who truly go along with the whole and most of those are in it to be able to do what they want to do, not to do what some other leftist faction tells them that they have to do, much less what kind of morality that we on the right have been advocating. The comic book store in San Francisco that is being hurt by the increase in the minimum wage there is an early example of this realization. What happens when you fight the institution as a populist movement and suddenly become the institution is that you must narrow your scope in the high offices to remain viable. Either you narrow it by going totalitarian, or you let yourself be replaced by moderates who promise the moon to everyone and sound believable. The "disenfranchised" who put their leaders in power will realize that they are now "disenfranchised" by their own leaders and pull the pendulum back in the other direction. By the time the pendulum swings back around, the next few generations have rejected their progenitors' obvious excesses. If a totalitarian state has come around, like what happened in China, then the ideological pendulum swing will be largely underground.
Cultural and political conservatives should study the turnaround at Southern Seminary in Louisville under Al Mohler to see a microcosm of the type of pendulum swing described in the linked article.