But a detailed review by The Post found that the chaotic events of Feb. 3 were years in the making, and that the responsibility extends beyond the local party leaders who have borne the brunt of the criticism.

Rather, the turmoil in Iowa reflected a systemic failure in which Democratic officials eager to avoid repeating the disastrous campaign of 2016 — marred by Russian hacks of party emails and allegations that the nominating process had been tilted against Sen. Bernie Sanders (I-Vt.) — oversaw changes that triggered a whole new crisis.

At the heart of the reforms would be a newly transparent caucus process, with raw vote totals announced publicly for the first time.

Party officials, however, never effectively vetted the basic tool used to collect and publish those results, the review found. They hardly questioned why an app was necessary, rather than a simpler reporting method, though internal correspondence shows that DNC staffers were privy to discussions about the testing and rollout of the technology.