1977: Watershed elections sweep Likud Party to power after years of consensus on the left. 1981: Likud Party wins elections. July 1984: Narrow Labor victory forces party to form coalition government with Likud. November 1988: Inconclusive national elections lead to the Likud and Labor coalition. May 14, 1989: Prime Minister Yitzhak Shamir presents his Middle East peace plan. Dec. 31, 1989: Mr. Shamir dismisses Ezer Weizman, the influential Labor Cabinet minister, for reportedly meeting with members of the Palestine Liberation Organization. Feb. 12, 1990: Ariel Sharon resigns from Cabinet and issues challenge to Shamir's leadership of the Likud Party. March 13: ``National unity'' government collapses when Labor Party leader Shimon Peres resigns and prompts the rest of Labor's Cabinet ministers to follow suit. April 26: Mr. Peres surrendered mandate to form government after five weeks of fruitless coalition bargaining. April 27: Shamir accepts mandate to form new Likud government.