Coolidge surprised many observers by announcing that he would not seek another term in August 1927. The decision left Hoover as the presumed front-runner for the 1928 presidential election, but many conservatives within the party opposed Hoover's candidacy. The conservative resistance to Hoover centered around Mellon, who controlled Pennsylvania's delegation at the 1928 Republican National Convention and was influential with Republicans throughout the country. Though they had maintained an amicable relationship in public, Mellon privately distrusted Hoover, resented Hoover's engagement in the affairs of other cabinet departments, and feared that a President Hoover would move away from Mellon's tax policies. Several Republicans urged Mellon to run for president, but Mellon believed that he was too old to seek the presidency. Mellon attempted to convince Coolidge or Charles Evans Hughes to run, but neither heeded his appeals. In the months before the 1928 Republican Convention, Mellon maintained his neutrality in the presidential race, but with no compelling alternative Republican candidate willing to run, Mellon finally threw his support behind Hoover. With Mellon's backing, Hoover won the Republican nomination on the first ballot of the convention, and he went on to defeat Al Smith in the 1928 presidential election. Defying widespread expectations that he would retire, Mellon chose to stay on as Secretary of the Treasury. Along with Secretary of Agriculture James Wilson and Secretary of Labor James J. Davis, Mellon is one of only three cabinet members to serve in the same post under three consecutive presidents.