Our Gemara on Amud Beis tells us that the World stands on Twelve pillars, then cites an opinion that it stands on seven pillars, and concludes with the opinion that it stands on only one pillar. That one pillar is known as the “Tzaddik Foundation of the World”.
Of course such cryptic statements beg interpretation. The Maharal Be’er Hagolah (6:8) explains that the material world can only be sustained from the spiritual forces flowing from God. These forces come from the pillars, that is the righteous humans who bring down the Divine flow.
The Twelve pillars are the Twelve Tribes, while the seven pillars are the three forefathers and four foremothers. However, ultimately that is not the final zechus. The final zechus is the Tzaddik who is presently living and active. In other words, the merits of the previous generations can only get you so far. At the end of the day, literally and figuratively, the world depends on a contemporary Tzaddik and this person (or even the idea of this person) is what holds the world up right now and brings down the divine flow.
Translations Courtesy of Sefaria, except when, sometimes, I disagree with the translation 
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