When Ben-Gurion resigned in June 1963, Eshkol was elected party chairman with a broad consensus and was subsequently appointed Prime Minister. However, his relationship with Ben-Gurion soon turned acrimonious over the latter's insistence on investigating the Lavon Affair, an Israeli covert operation in Egypt, which had gone wrong a decade earlier. Ben-Gurion failed to challenge Eshkol's leadership and split from Mapai with a few of his young protégés to form Rafi in June 1965. In the meantime, Mapai merged with Ahdut HaAvoda to form the Alignment with Eshkol as its head. Rafi was defeated by the Alignment in the elections held in November 1965, establishing Eshkol as the country's indisputable leader. Yet Ben-Gurion, drawing on his influence as Israel's founding father, continued to undermine Eshkol's authority throughout his term as Prime Minister, portraying him as a spineless politician incapable of addressing Israel's security predicament.