On this day in 1940, President Franklin D. Roosevelt was nominated as the Democratic Party's candidate for the presidency, after already having served two terms. He would become the only president to serve more than two terms, being elected president a total of four times (something that would be illegal today). He had already instituted his New Deal programs by 1940 and remained popular, despite some pushback on some of his bigger policies. The race for the presidency between Roosevelt and the Republican candidate Wendell Wilkie was close—but Roosevelt had a card up his sleeve.
The issue of the day was Germany, whose forces were sweeping through Western Europe. The United Kingdom, a close ally, was under threat. Roosevelt was determined to steer the U.S. through the conflict, thinking nobody else had the skills necessary to do so. The public was nervous about the German invasions, and Roosevelt was positioned to do something about it. He announced an agreement to rearm and aid the U.K., meeting the concerns of Americans and effectively guaranteeing his re-election to a third term. Ah, the powers of incumbency.
You can read more about Roosevelt's nomination for a third term in this article from the New York Times archives.