In the wake of celebrations surrounding Constitution Day, Atlantic readers encounter Yoni Applebaum’s thought-provoking piece about the document’s long-term utility.

Even if we discount the failures of other presidential democracies, though, we should not dismiss the fact that the U.S. Constitution was modeled on a system that collapsed into civil war, and that it is inherently fragile. “This is a system that requires a particular set of political norms,” Eric Nelson told me, “and it can be very dangerous and dysfunctional where those norms are not present.” Once those norms have been discarded, the president or either house of Congress can simply go on strike, refusing to fulfill their responsibilities. Nothing can compel them to act.

Until recently, American politicians have generally made the compromises necessary to govern. The trouble is that cultures evolve. As American politics grows increasingly polarized, the goodwill that oiled the system and helped it function smoothly disappears. In 2013, fights over the debt ceiling and funding for the Affordable Care Act very nearly produced a constitutional crisis. Congress and the president each refused to yield, and the government shut down for 16 days. In November 2014, claiming that he was “acting where Congress has failed,” President Obama announced a series of executive actions on immigration. House Republicans denounced him as “threatening to unravel our system of checks and balances” and warned that they would cut off funding for the Department of Homeland Security unless Obama’s actions were rolled back. For months, the two sides faced off, pledging fealty to the Constitution even as they exposed its flaws. Only at the 11th hour did the House pull back from the edge.

Strikingly, in these and other recent crises, public opinion has tended to favor the president. As governments deadlock, executives are inclined to act unilaterally, thereby deepening crises. When parliament refused to provide Charles I with funds unless he met its demands, he moved to circumvent the legislators, and they in turn deposed him. Other presidential systems have collapsed in much the same way.

The Framers do not seem to have understood this particular flaw of mixed monarchy. But then, neither did they express absolute faith in their own wisdom. “They were incredibly conscious of the fragility of what they were creating,” Nelson says, “that it depends on forbearance.” The Constitution was an experiment, and its signers believed that its success was contingent on the willingness of varied constituencies to work together.