Zechus Avos (ancestral merit) - does it still exist?

Garnel Ironheart commented:

DaatTorah, I think I can help you out. The gemara says we ran out of zechus Avos a long time ago so you can put a passing footnote in and move on.

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The gemora does in fact state that zechos avos stopped sometime during the First Temple:

Shabbos(55a): Samuel said: The taw denotes, the merit of the Patriarchs is exhausted [tamah].19 R. Johanan said: The merit of the Patriarchs will confer grace [tahon].[ (20) Samuel explains the taw on the wicked; R. Johanan that on the righteous.] …. And since when has the merit of the Patriarchs been exhausted? — Rab said, Since the days of Hosea the son of Beeri, for it is written, [And now] will I discover her lewdness in the sight of her lovers, and none shall deliver her out of mine hand.22 Samuel said. Since the days of Hazael, for it is said, And Hazael king of Syria oppressed Israel all the days of Jehoahaz;23 and it is written, But the Lord was gracious unto them, and had compassion upon them, and had respect unto them, because of the covenant with Abraham, Isaac, and Jacob, and would not destroy them, neither cast he them from his presence until now.24 R. Joshua b. Levi said: Since the days of Elijah, for it is said, And it came to pass at the time of the offering of the evening oblation, that Elijah the prophet came near, and said, O Lord, the God of Abraham, of Isaac, and of Israel, let it be known this day that thou art God in Israel, and that I am thy servant, and that I have done all these things at thy word.25 [25) I Kings XVIII, 36. Here too this day implies a limitation.] R. Johanan said: Since the days of Hezekiah, for it is said, Of the increase of his government and of peace there shall be no end, upon the throne of David, and upon his kingdom, to establish it, and to uphold it with judgement and with righteousness for henceforth even for ever. The zeal of the Lord of hosts shall perform this.26 [Isa. IX, 6. ‘The zeal, etc.’ implies, but not the merit of the Patriarchs, this being exhausted by now.]

However we have

Vayikra Rabbah(36:6):. How long did the merit of the Patriarchs endure? R. Tanhuma said in the name of R. Hiyya b. Menahma, or, as some say, R. Berekiah b. Helbo said it in the name of Rabba b. Zabda: Until Jehoahaz. This is proved by the text, But the Lord was gracious unto them, and had compassion on them... because of His covenant with Abraham, Isaac, and Jacob and would not destroy them... until now (II Kings XIII, 23), as much as to say, ’until now’ the merit of the Patriarchs has endured. R. Joshua b. Levi says: Until Elijah. This is proved by the text, And it came to pass at the time of the offering of the evening offering, that Elijah the prophet came near, and said: O Lord the God of Abraham, of Isaac and of Israel (I Kings XVIII, 36). Samuel said: Until Hosea. This is proved by the text, And now will I uncover her shame in the sight of her lovers, and none (ish) shall deliver her out of My hand (Hosea II, 12); ’ish’ in the present context signifying Abraham, as may be inferred from the citation, Now therefore restore the man's (ish) wife (Gen. XX, 7); ’ish’ also signifies Isaac, as it says, What man (ish) is this? (ib. XXIV, 65); and ’ish’ also signifies Jacob, as it says, Jacob was a quiet man--ish (ib. XXV, 27). R. Judan says: Until Hezekiah. This may be proved by the citation: That the government may be increased, and of peace there be no end... The zeal of the Lord of hosts1 doth perform this (Isa. IX, 6). R. Judan b. Rabbi in the name of R. Berekiah said: If you see that the merit of the Patriarchs is failing and the merit of the Matriarchs slipping away, go and occupy yourself with benevolence [love]. This is borne out by the text, For the mountains may depart and the hills be removed; but My love shall not depart from thee (ib. LIV, 10); ’mountains’ signify the Patriarchs, ’hills’ the Matriarchs, and after that ’My love shall not depart from thee’.2 R. Acha said: The merit of the Patriarchs shall endure for ever. We shall always mention them and say: For the Lord thy God is a merciful God; He will not fail thee, neither destroy thee, nor forget the covenant of thy fathers, etc. (Deut. V, 31)

Ohr Zarua(2:23) says we poken like the above view of R' Acha against the view of the Bavli

However we have another Bavli which clearly states that zechus avos did not end in the First Temple. This is the incident where R' Gamliel was replace by R' Eleazar ben Azariah.

Berachos (27b ): Come, let us depose him! Whom shall we appoint instead? We can hardly appoint R. Joshua, because he is one of the parties involved. We can hardly appoint R. Akiba because perhaps Rabban Gamaliel will bring a curse on him because he has no zechus avos. Let us then appoint R. Eleazar b. Azariah, who is wise and rich and the tenth in descent from Ezra. He is wise, so that if anyone puts a question to him he will be able to answer it. He is rich, so that if occasion arises for paying court19 to Caesar he will be able to do so. He is tenth in descent from Ezra, so that he has zechus avos and he [Rabban Gamaliel] cannot bring a curse on him.