Accordance is agreement between people or consensus within a group. A lack of accordance between members of a political party can spell disaster for their presidential candidate.
Accordance comes from the Old French acorder, meaning "bring to an agreement." When two things are in accordance, they fit together harmoniously. You'll usually see accordance in the phrase "in accordance with," as when you command your kid brother, "act in accordance with my wishes, or face the consequences!" It's most often used to show that someone is following rules or regulations.