In issuing the Monroe Doctrine, the United States displayed a new level of assertiveness in international relations, as the doctrine represented the country's first claim to a sphere of influence. It also marked the country's shift in psychological orientation away from Europe and towards the Americas. Debates over foreign policy would no longer center on relations with Britain and France, but would instead focus on western expansion and relations with Native Americans. The doctrine became one of the foundational principles of U.S. foreign policy. Immediately upon becoming Secretary of State, Adams emerged as one of Monroe's most likely successors, as the last three presidents had all served in the role at some point before taking office. Though he lacked the charisma of his competitors, Adams was widely respected and benefited from the lack of other prominent Northern political leaders.Adams's top choice for the role of vice president was General Andrew Jackson; Adams noted that 'the Vice-Presidency was a station in which [Jackson] could hang no one, and in which he would need to quarrel with no one.'