[91] On September 24, 1955, President Eisenhower suffered a heart attack and his condition was initially believed to be life-threatening. Eisenhower was unable to perform his duties for six weeks. The 25th Amendment to the United States Constitution had not yet been proposed, and the vice president had no formal power to act. Nonetheless, Nixon acted in Eisenhower's stead during this period, presiding over Cabinet meetings and ensuring that aides and Cabinet officers did not seek power.[92] According to Nixon biographer Stephen Ambrose, Nixon had "earned the high praise he received for his conduct during the crisis ... he made no attempt to seize power".[93]
His spirits buoyed, Nixon sought a second term, but some of Eisenhower's aides aimed to displace him. In a December 1955 meeting, Eisenhower proposed that Nixon not run for reelection and instead become a Cabinet officer in a second Eisenhower administration, in order to give him administrative experience before a 1960 presidential run. Nixon believed this would destroy his political career. When Eisenhower announced his reelection bid in February 1956, he hedged on the choice of his running mate, saying it was improper to address that question until he had been renominated. 