The election took place against a backdrop of a world in turmoil. Close to home, Mexico was going through the Mexican Revolution, while in Europe World War I was in its third year. Public sentiment at home was split between those who wanted their nation to remain neutral in the European conflict, and those who leaned towards the British and French (Allied) forces, due to the harsh treatment of civilians by the German Army in large parts of Belgium and northern France. It appeared that the majority of American voters wanted to avoid involvement in the war, and preferred the policy of neutrality. Wilson's campaign used the popular slogan "He kept us out of war" to appeal to those voters who wanted to avoid a war in Europe or with Mexico.
For the Republicans, the first order of the day was reuniting their party and heal the bitter split that had occurred in the 1912 presidential campaign. Several candidates were openly competing for the 1916 nomination as the Republican convention approached. Two of the most prominent candidates were conservative Senator Elihu Root of New York and liberal Senator John W. Weeks of Massachusetts.
Root had an impressive resume. He had served as the Secretary of War from 1899 to 1904 under Presidents William McKinley and Theodore Roosevelt. He was elected by the state legislature as a U.S. Senator from New York and served one term, 1909–1915. During that time Root was awarded the Nobel Peace Prize in 1912. Root had been a supporter of William Howard Taft during the previous election. Although he was considered by many as a Washington "wise man", Root was 71 years of age at the time of the convention, and his age and his ties to one faction were both seen as impediments to his nomination.
Weeks had been the the Mayor of Newton, Massachusetts from 1902 to 1903, a United States Representative for Massachusetts from 1905 to 1913, as a United States Senator since 1913. Like Root, the knock on Weeks was that he was acceptable only to one faction of the party and could not unite the Republicans in their fight against Wilson. Party bosses wanted a moderate who would be acceptable to both factions of the party.
The one name the party bosses could agree on was Supreme Court Justice Charles Evan Hughes. He was widely seen having the ability to unite the party. He had served as the 36th Governor of New York from 1907 to 1910, when he was appointed as an Associate Justice of the Supreme Court of the United States by Taft. Other potential dark horse candidates included Massachusetts Senator Henry Cabot Lodge or General Leonard Wood, though both men had close ties to Roosevelt. Many Republicans saw this as a good strategy because they believed that if they could nominate a candidate acceptable to Roosevelt, this would averting another third party run by progressive Republicans. Former Vice President Charles Fairbanks also saw himself as a viable candidate and he attempted to curry Roosevelt's support, but Roosevelt refused to support Fairbanks.
When the convention met in Chicago from June 7 to 10 of 1916, Hughes led on every ballot. On the first ballot he led by 253.5 votes, with Weeks in second with 105, Root in third with 103, Roosevelt in fourth with 85, Congressman Theodore Burton of Ohio in fifth with 77.5 and Fairbanks in sixth with 74.5. Hughes gained votes on the second ballot and on the third he won the nomination, receiving 949.5 votes.
Fairbanks, who had served as Vice-President under Roosevelt, claimed he was not interested in holding the office again, but when the party nominated him as Hughes' running mate, he accepted the position.
The Progressive Party re-nominated former President Theodore Roosevelt and nominated John Parker of Louisiana as his running-mate. However, Roosevelt telegraphed the convention and declared that he could not accept their nomination and would be endorsing Hughes for the Presidency. When the Progressive Party National Committee met in Chicago on June 26, those in attendance reluctantly endorsed Hughes.
During the election campaign that followed, the Democrats used the pro-Wilson slogan, "He Kept Us out of War," and told voters that a Republican victory would mean war with both Mexico and Germany. Hughes opted to downplay the war as an issue. He advocated a program of greater preparedness. Wilson was believed to have successfully pressured the Germans to suspend unrestricted submarine warfare, making it difficult for Hughes to attack Wilson's peace platform. Instead, Hughes attacked Wilson for his support of various "pro-labor" laws, such as limiting the workday to eight hours, on the grounds that they were harmful to business interests. His criticisms gained little support, especially among factory workers who supported such laws.
Hughes was helped by the vigorous support of popular former President Theodore Roosevelt, but he made a key mistake in California when, just before the election, Hughes made a campaign swing through the state, but never met with the powerful Republican Governor Hiram Johnson to seek his support. Johnson took this as a snub and did not campaign for Hughes. Wilson ended up winning the state, which made all the difference in the final result.
The result was exceptionally close and the outcome remained in doubt for several days, partially because of the wait for returns from California. The electoral vote was one of the closest in history. 266 votes were needed to win. In the end Wilson won 30 states for 277 electoral votes, while Hughes won 18 states and 254 electoral votes.