Under the Articles of Confederation, the U.S could not borrow money, engage in war, or appoint a commander in chief of army/navy without the approval of 9 of the states.
The Constitution created a judicial branch headed by the Supreme Court to settle federal government disputes, disputes between states, and with foreign affairs.
The Constitution established the "necessary and proper clause" or "elastic clause", which allowed the federal government to enact laws to carry out its enumerated/implied powers.
Electoral behavior of U.S. voters can be examined by party identification, candidate characteristics, political issues of the time, and by ethnic/racial groups.