The U.S. Constitution left the method of selecting electors up the states, so methods vary. Generally, the political parties nominate electors at their state party conventions (in thirty-six states) or by a vote of the party’s central committee in each state (in ten states). Aside from members of Congress and employees of the federal government, who are prohibited from serving as an elector in order to maintain the balance between the legislative and executive branches of the federal government, anyone may serve as an elector. Since electors are often selected in recognition of their service and dedication to their political party, they are often state-elected officials, party leaders, or persons who have a personal or political affiliation with the presidential candidate. Today, all states choose their electors by direct statewide election, except for Maine and Nebraska.